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14db069468
The two folding operations are causing a cycle for the following case
with
scalable vector types:
define <vscale x 2 x double> @test_fneg_select_abs(<vscale x 2 x i1>
%cond, <vscale x 2 x double> %b) {
%1 = select <vscale x 2 x i1> %cond, <vscale x 2 x double>
zeroinitializer, <vscale x 2 x double> %b
%2 = fneg fast <vscale x 2 x double> %1
ret <vscale x 2 x double> %2
}
1) fold fneg: -(Cond ? C : Y) -> Cond ? -C : -Y
2) fold select: (Cond ? -X : -Y) -> -(Cond ? X : Y)
1) results in the following since '<vscale x 2 x double>
zeroinitializer' passes
the check for the immediate constant:
%.neg = fneg fast <vscale x 2 x double> zeroinitializer
%b.neg = fneg fast <vscale x 2 x double> %b
%1 = select fast <vscale x 2 x i1> %cond, <vscale x 2 x double> %.neg,
<vscale x 2 x double> %b.neg
and so we end up going back and forth between 1) and 2).
Attempt to fold scalable vector constants, so that we end up with a
splat instead:
define <vscale x 2 x double> @test_fneg_select_abs(<vscale x 2 x i1>
%cond, <vscale x 2 x double> %b) {
%b.neg = fneg fast <vscale x 2 x double> %b
%1 = select fast <vscale x 2 x i1> %cond, <vscale x 2 x double>
shufflevector (<vscale x 2 x double> insertelement (<vscale x 2 x
double> poison, double -0.000000e+00, i64 0), <vscale x 2 x double>
poison, <vscale x 2 x i32> zeroinitializer), <vscale x 2 x double>
%b.neg
ret <vscale x 2 x double> %1
}
1357 lines
52 KiB
C++
1357 lines
52 KiB
C++
//===- ConstantFold.cpp - LLVM constant folder ----------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements folding of constants for LLVM. This implements the
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// (internal) ConstantFold.h interface, which is used by the
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// ConstantExpr::get* methods to automatically fold constants when possible.
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//
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// The current constant folding implementation is implemented in two pieces: the
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// pieces that don't need DataLayout, and the pieces that do. This is to avoid
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// a dependence in IR on Target.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/IR/ConstantFold.h"
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#include "llvm/ADT/APSInt.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/GetElementPtrTypeIterator.h"
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#include "llvm/IR/GlobalAlias.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/Operator.h"
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#include "llvm/IR/PatternMatch.h"
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#include "llvm/Support/ErrorHandling.h"
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using namespace llvm;
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using namespace llvm::PatternMatch;
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//===----------------------------------------------------------------------===//
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// ConstantFold*Instruction Implementations
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//===----------------------------------------------------------------------===//
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/// This function determines which opcode to use to fold two constant cast
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/// expressions together. It uses CastInst::isEliminableCastPair to determine
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/// the opcode. Consequently its just a wrapper around that function.
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/// Determine if it is valid to fold a cast of a cast
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static unsigned
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foldConstantCastPair(
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unsigned opc, ///< opcode of the second cast constant expression
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ConstantExpr *Op, ///< the first cast constant expression
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Type *DstTy ///< destination type of the first cast
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) {
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assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!");
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assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type");
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assert(CastInst::isCast(opc) && "Invalid cast opcode");
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// The types and opcodes for the two Cast constant expressions
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Type *SrcTy = Op->getOperand(0)->getType();
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Type *MidTy = Op->getType();
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Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode());
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Instruction::CastOps secondOp = Instruction::CastOps(opc);
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// Assume that pointers are never more than 64 bits wide, and only use this
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// for the middle type. Otherwise we could end up folding away illegal
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// bitcasts between address spaces with different sizes.
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IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext());
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// Let CastInst::isEliminableCastPair do the heavy lifting.
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return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy,
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nullptr, FakeIntPtrTy, nullptr);
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}
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static Constant *FoldBitCast(Constant *V, Type *DestTy) {
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Type *SrcTy = V->getType();
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if (SrcTy == DestTy)
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return V; // no-op cast
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// Handle casts from one vector constant to another. We know that the src
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// and dest type have the same size (otherwise its an illegal cast).
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if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) {
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if (V->isAllOnesValue())
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return Constant::getAllOnesValue(DestTy);
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// Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts
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// This allows for other simplifications (although some of them
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// can only be handled by Analysis/ConstantFolding.cpp).
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if (!isa<VectorType>(SrcTy))
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if (isa<ConstantInt>(V) || isa<ConstantFP>(V))
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return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy);
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return nullptr;
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}
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// Handle integral constant input.
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
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// See note below regarding the PPC_FP128 restriction.
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if (DestTy->isFloatingPointTy() && !DestTy->isPPC_FP128Ty())
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return ConstantFP::get(DestTy->getContext(),
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APFloat(DestTy->getFltSemantics(),
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CI->getValue()));
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// Otherwise, can't fold this (vector?)
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return nullptr;
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}
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// Handle ConstantFP input: FP -> Integral.
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if (ConstantFP *FP = dyn_cast<ConstantFP>(V)) {
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// PPC_FP128 is really the sum of two consecutive doubles, where the first
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// double is always stored first in memory, regardless of the target
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// endianness. The memory layout of i128, however, depends on the target
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// endianness, and so we can't fold this without target endianness
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// information. This should instead be handled by
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// Analysis/ConstantFolding.cpp
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if (FP->getType()->isPPC_FP128Ty())
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return nullptr;
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// Make sure dest type is compatible with the folded integer constant.
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if (!DestTy->isIntegerTy())
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return nullptr;
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return ConstantInt::get(FP->getContext(),
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FP->getValueAPF().bitcastToAPInt());
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}
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return nullptr;
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}
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static Constant *foldMaybeUndesirableCast(unsigned opc, Constant *V,
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Type *DestTy) {
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return ConstantExpr::isDesirableCastOp(opc)
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? ConstantExpr::getCast(opc, V, DestTy)
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: ConstantFoldCastInstruction(opc, V, DestTy);
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}
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Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
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Type *DestTy) {
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if (isa<PoisonValue>(V))
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return PoisonValue::get(DestTy);
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if (isa<UndefValue>(V)) {
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// zext(undef) = 0, because the top bits will be zero.
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// sext(undef) = 0, because the top bits will all be the same.
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// [us]itofp(undef) = 0, because the result value is bounded.
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if (opc == Instruction::ZExt || opc == Instruction::SExt ||
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opc == Instruction::UIToFP || opc == Instruction::SIToFP)
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return Constant::getNullValue(DestTy);
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return UndefValue::get(DestTy);
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}
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if (V->isNullValue() && !DestTy->isX86_AMXTy() &&
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opc != Instruction::AddrSpaceCast)
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return Constant::getNullValue(DestTy);
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// If the cast operand is a constant expression, there's a few things we can
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// do to try to simplify it.
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if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
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if (CE->isCast()) {
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// Try hard to fold cast of cast because they are often eliminable.
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if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy))
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return foldMaybeUndesirableCast(newOpc, CE->getOperand(0), DestTy);
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}
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}
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// If the cast operand is a constant vector, perform the cast by
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// operating on each element. In the cast of bitcasts, the element
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// count may be mismatched; don't attempt to handle that here.
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if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) &&
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DestTy->isVectorTy() &&
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cast<FixedVectorType>(DestTy)->getNumElements() ==
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cast<FixedVectorType>(V->getType())->getNumElements()) {
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VectorType *DestVecTy = cast<VectorType>(DestTy);
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Type *DstEltTy = DestVecTy->getElementType();
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// Fast path for splatted constants.
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if (Constant *Splat = V->getSplatValue()) {
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Constant *Res = foldMaybeUndesirableCast(opc, Splat, DstEltTy);
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if (!Res)
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return nullptr;
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return ConstantVector::getSplat(
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cast<VectorType>(DestTy)->getElementCount(), Res);
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}
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SmallVector<Constant *, 16> res;
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Type *Ty = IntegerType::get(V->getContext(), 32);
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for (unsigned i = 0,
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e = cast<FixedVectorType>(V->getType())->getNumElements();
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i != e; ++i) {
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Constant *C = ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i));
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Constant *Casted = foldMaybeUndesirableCast(opc, C, DstEltTy);
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if (!Casted)
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return nullptr;
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res.push_back(Casted);
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}
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return ConstantVector::get(res);
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}
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// We actually have to do a cast now. Perform the cast according to the
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// opcode specified.
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switch (opc) {
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default:
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llvm_unreachable("Failed to cast constant expression");
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case Instruction::FPTrunc:
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case Instruction::FPExt:
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if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
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bool ignored;
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APFloat Val = FPC->getValueAPF();
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Val.convert(DestTy->getFltSemantics(), APFloat::rmNearestTiesToEven,
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&ignored);
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return ConstantFP::get(V->getContext(), Val);
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}
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return nullptr; // Can't fold.
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case Instruction::FPToUI:
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case Instruction::FPToSI:
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if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) {
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const APFloat &V = FPC->getValueAPF();
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bool ignored;
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uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
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APSInt IntVal(DestBitWidth, opc == Instruction::FPToUI);
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if (APFloat::opInvalidOp ==
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V.convertToInteger(IntVal, APFloat::rmTowardZero, &ignored)) {
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// Undefined behavior invoked - the destination type can't represent
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// the input constant.
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return PoisonValue::get(DestTy);
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}
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return ConstantInt::get(FPC->getContext(), IntVal);
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}
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return nullptr; // Can't fold.
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case Instruction::UIToFP:
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case Instruction::SIToFP:
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
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const APInt &api = CI->getValue();
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APFloat apf(DestTy->getFltSemantics(),
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APInt::getZero(DestTy->getPrimitiveSizeInBits()));
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apf.convertFromAPInt(api, opc==Instruction::SIToFP,
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APFloat::rmNearestTiesToEven);
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return ConstantFP::get(V->getContext(), apf);
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}
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return nullptr;
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case Instruction::ZExt:
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
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uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
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return ConstantInt::get(V->getContext(),
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CI->getValue().zext(BitWidth));
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}
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return nullptr;
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case Instruction::SExt:
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
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uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth();
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return ConstantInt::get(V->getContext(),
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CI->getValue().sext(BitWidth));
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}
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return nullptr;
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case Instruction::Trunc: {
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if (V->getType()->isVectorTy())
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return nullptr;
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uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth();
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if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
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return ConstantInt::get(V->getContext(),
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CI->getValue().trunc(DestBitWidth));
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}
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return nullptr;
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}
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case Instruction::BitCast:
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return FoldBitCast(V, DestTy);
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case Instruction::AddrSpaceCast:
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case Instruction::IntToPtr:
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case Instruction::PtrToInt:
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return nullptr;
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}
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}
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Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
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Constant *V1, Constant *V2) {
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// Check for i1 and vector true/false conditions.
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if (Cond->isNullValue()) return V2;
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if (Cond->isAllOnesValue()) return V1;
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// If the condition is a vector constant, fold the result elementwise.
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if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) {
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auto *V1VTy = CondV->getType();
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SmallVector<Constant*, 16> Result;
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Type *Ty = IntegerType::get(CondV->getContext(), 32);
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for (unsigned i = 0, e = V1VTy->getNumElements(); i != e; ++i) {
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Constant *V;
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Constant *V1Element = ConstantExpr::getExtractElement(V1,
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ConstantInt::get(Ty, i));
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Constant *V2Element = ConstantExpr::getExtractElement(V2,
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ConstantInt::get(Ty, i));
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auto *Cond = cast<Constant>(CondV->getOperand(i));
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if (isa<PoisonValue>(Cond)) {
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V = PoisonValue::get(V1Element->getType());
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} else if (V1Element == V2Element) {
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V = V1Element;
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} else if (isa<UndefValue>(Cond)) {
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V = isa<UndefValue>(V1Element) ? V1Element : V2Element;
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} else {
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if (!isa<ConstantInt>(Cond)) break;
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V = Cond->isNullValue() ? V2Element : V1Element;
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}
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Result.push_back(V);
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}
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// If we were able to build the vector, return it.
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if (Result.size() == V1VTy->getNumElements())
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return ConstantVector::get(Result);
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}
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if (isa<PoisonValue>(Cond))
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return PoisonValue::get(V1->getType());
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if (isa<UndefValue>(Cond)) {
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if (isa<UndefValue>(V1)) return V1;
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return V2;
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}
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if (V1 == V2) return V1;
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if (isa<PoisonValue>(V1))
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return V2;
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if (isa<PoisonValue>(V2))
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return V1;
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// If the true or false value is undef, we can fold to the other value as
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// long as the other value isn't poison.
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auto NotPoison = [](Constant *C) {
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if (isa<PoisonValue>(C))
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return false;
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// TODO: We can analyze ConstExpr by opcode to determine if there is any
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// possibility of poison.
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if (isa<ConstantExpr>(C))
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return false;
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if (isa<ConstantInt>(C) || isa<GlobalVariable>(C) || isa<ConstantFP>(C) ||
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isa<ConstantPointerNull>(C) || isa<Function>(C))
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return true;
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if (C->getType()->isVectorTy())
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return !C->containsPoisonElement() && !C->containsConstantExpression();
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// TODO: Recursively analyze aggregates or other constants.
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return false;
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};
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if (isa<UndefValue>(V1) && NotPoison(V2)) return V2;
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if (isa<UndefValue>(V2) && NotPoison(V1)) return V1;
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return nullptr;
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}
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Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val,
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Constant *Idx) {
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auto *ValVTy = cast<VectorType>(Val->getType());
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// extractelt poison, C -> poison
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// extractelt C, undef -> poison
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if (isa<PoisonValue>(Val) || isa<UndefValue>(Idx))
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return PoisonValue::get(ValVTy->getElementType());
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// extractelt undef, C -> undef
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if (isa<UndefValue>(Val))
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return UndefValue::get(ValVTy->getElementType());
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auto *CIdx = dyn_cast<ConstantInt>(Idx);
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if (!CIdx)
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return nullptr;
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if (auto *ValFVTy = dyn_cast<FixedVectorType>(Val->getType())) {
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// ee({w,x,y,z}, wrong_value) -> poison
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if (CIdx->uge(ValFVTy->getNumElements()))
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return PoisonValue::get(ValFVTy->getElementType());
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}
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// ee (gep (ptr, idx0, ...), idx) -> gep (ee (ptr, idx), ee (idx0, idx), ...)
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if (auto *CE = dyn_cast<ConstantExpr>(Val)) {
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if (auto *GEP = dyn_cast<GEPOperator>(CE)) {
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SmallVector<Constant *, 8> Ops;
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Ops.reserve(CE->getNumOperands());
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for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) {
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Constant *Op = CE->getOperand(i);
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if (Op->getType()->isVectorTy()) {
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Constant *ScalarOp = ConstantExpr::getExtractElement(Op, Idx);
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if (!ScalarOp)
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return nullptr;
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Ops.push_back(ScalarOp);
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} else
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Ops.push_back(Op);
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}
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return CE->getWithOperands(Ops, ValVTy->getElementType(), false,
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GEP->getSourceElementType());
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} else if (CE->getOpcode() == Instruction::InsertElement) {
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if (const auto *IEIdx = dyn_cast<ConstantInt>(CE->getOperand(2))) {
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if (APSInt::isSameValue(APSInt(IEIdx->getValue()),
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APSInt(CIdx->getValue()))) {
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return CE->getOperand(1);
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} else {
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return ConstantExpr::getExtractElement(CE->getOperand(0), CIdx);
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}
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}
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}
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}
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if (Constant *C = Val->getAggregateElement(CIdx))
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return C;
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// Lane < Splat minimum vector width => extractelt Splat(x), Lane -> x
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if (CIdx->getValue().ult(ValVTy->getElementCount().getKnownMinValue())) {
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if (Constant *SplatVal = Val->getSplatValue())
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return SplatVal;
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}
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return nullptr;
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}
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Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,
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Constant *Elt,
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Constant *Idx) {
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if (isa<UndefValue>(Idx))
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return PoisonValue::get(Val->getType());
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// Inserting null into all zeros is still all zeros.
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// TODO: This is true for undef and poison splats too.
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if (isa<ConstantAggregateZero>(Val) && Elt->isNullValue())
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return Val;
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ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
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if (!CIdx) return nullptr;
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// Do not iterate on scalable vector. The num of elements is unknown at
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// compile-time.
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if (isa<ScalableVectorType>(Val->getType()))
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return nullptr;
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auto *ValTy = cast<FixedVectorType>(Val->getType());
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unsigned NumElts = ValTy->getNumElements();
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if (CIdx->uge(NumElts))
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return PoisonValue::get(Val->getType());
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SmallVector<Constant*, 16> Result;
|
|
Result.reserve(NumElts);
|
|
auto *Ty = Type::getInt32Ty(Val->getContext());
|
|
uint64_t IdxVal = CIdx->getZExtValue();
|
|
for (unsigned i = 0; i != NumElts; ++i) {
|
|
if (i == IdxVal) {
|
|
Result.push_back(Elt);
|
|
continue;
|
|
}
|
|
|
|
Constant *C = ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i));
|
|
Result.push_back(C);
|
|
}
|
|
|
|
return ConstantVector::get(Result);
|
|
}
|
|
|
|
Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, Constant *V2,
|
|
ArrayRef<int> Mask) {
|
|
auto *V1VTy = cast<VectorType>(V1->getType());
|
|
unsigned MaskNumElts = Mask.size();
|
|
auto MaskEltCount =
|
|
ElementCount::get(MaskNumElts, isa<ScalableVectorType>(V1VTy));
|
|
Type *EltTy = V1VTy->getElementType();
|
|
|
|
// Poison shuffle mask -> poison value.
|
|
if (all_of(Mask, [](int Elt) { return Elt == PoisonMaskElem; })) {
|
|
return PoisonValue::get(VectorType::get(EltTy, MaskEltCount));
|
|
}
|
|
|
|
// If the mask is all zeros this is a splat, no need to go through all
|
|
// elements.
|
|
if (all_of(Mask, [](int Elt) { return Elt == 0; })) {
|
|
Type *Ty = IntegerType::get(V1->getContext(), 32);
|
|
Constant *Elt =
|
|
ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, 0));
|
|
|
|
if (Elt->isNullValue()) {
|
|
auto *VTy = VectorType::get(EltTy, MaskEltCount);
|
|
return ConstantAggregateZero::get(VTy);
|
|
} else if (!MaskEltCount.isScalable())
|
|
return ConstantVector::getSplat(MaskEltCount, Elt);
|
|
}
|
|
|
|
// Do not iterate on scalable vector. The num of elements is unknown at
|
|
// compile-time.
|
|
if (isa<ScalableVectorType>(V1VTy))
|
|
return nullptr;
|
|
|
|
unsigned SrcNumElts = V1VTy->getElementCount().getKnownMinValue();
|
|
|
|
// Loop over the shuffle mask, evaluating each element.
|
|
SmallVector<Constant*, 32> Result;
|
|
for (unsigned i = 0; i != MaskNumElts; ++i) {
|
|
int Elt = Mask[i];
|
|
if (Elt == -1) {
|
|
Result.push_back(UndefValue::get(EltTy));
|
|
continue;
|
|
}
|
|
Constant *InElt;
|
|
if (unsigned(Elt) >= SrcNumElts*2)
|
|
InElt = UndefValue::get(EltTy);
|
|
else if (unsigned(Elt) >= SrcNumElts) {
|
|
Type *Ty = IntegerType::get(V2->getContext(), 32);
|
|
InElt =
|
|
ConstantExpr::getExtractElement(V2,
|
|
ConstantInt::get(Ty, Elt - SrcNumElts));
|
|
} else {
|
|
Type *Ty = IntegerType::get(V1->getContext(), 32);
|
|
InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt));
|
|
}
|
|
Result.push_back(InElt);
|
|
}
|
|
|
|
return ConstantVector::get(Result);
|
|
}
|
|
|
|
Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg,
|
|
ArrayRef<unsigned> Idxs) {
|
|
// Base case: no indices, so return the entire value.
|
|
if (Idxs.empty())
|
|
return Agg;
|
|
|
|
if (Constant *C = Agg->getAggregateElement(Idxs[0]))
|
|
return ConstantFoldExtractValueInstruction(C, Idxs.slice(1));
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
|
|
Constant *Val,
|
|
ArrayRef<unsigned> Idxs) {
|
|
// Base case: no indices, so replace the entire value.
|
|
if (Idxs.empty())
|
|
return Val;
|
|
|
|
unsigned NumElts;
|
|
if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
|
|
NumElts = ST->getNumElements();
|
|
else
|
|
NumElts = cast<ArrayType>(Agg->getType())->getNumElements();
|
|
|
|
SmallVector<Constant*, 32> Result;
|
|
for (unsigned i = 0; i != NumElts; ++i) {
|
|
Constant *C = Agg->getAggregateElement(i);
|
|
if (!C) return nullptr;
|
|
|
|
if (Idxs[0] == i)
|
|
C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1));
|
|
|
|
Result.push_back(C);
|
|
}
|
|
|
|
if (StructType *ST = dyn_cast<StructType>(Agg->getType()))
|
|
return ConstantStruct::get(ST, Result);
|
|
return ConstantArray::get(cast<ArrayType>(Agg->getType()), Result);
|
|
}
|
|
|
|
Constant *llvm::ConstantFoldUnaryInstruction(unsigned Opcode, Constant *C) {
|
|
assert(Instruction::isUnaryOp(Opcode) && "Non-unary instruction detected");
|
|
|
|
// Handle scalar UndefValue and scalable vector UndefValue. Fixed-length
|
|
// vectors are always evaluated per element.
|
|
bool IsScalableVector = isa<ScalableVectorType>(C->getType());
|
|
bool HasScalarUndefOrScalableVectorUndef =
|
|
(!C->getType()->isVectorTy() || IsScalableVector) && isa<UndefValue>(C);
|
|
|
|
if (HasScalarUndefOrScalableVectorUndef) {
|
|
switch (static_cast<Instruction::UnaryOps>(Opcode)) {
|
|
case Instruction::FNeg:
|
|
return C; // -undef -> undef
|
|
case Instruction::UnaryOpsEnd:
|
|
llvm_unreachable("Invalid UnaryOp");
|
|
}
|
|
}
|
|
|
|
// Constant should not be UndefValue, unless these are vector constants.
|
|
assert(!HasScalarUndefOrScalableVectorUndef && "Unexpected UndefValue");
|
|
// We only have FP UnaryOps right now.
|
|
assert(!isa<ConstantInt>(C) && "Unexpected Integer UnaryOp");
|
|
|
|
if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
|
|
const APFloat &CV = CFP->getValueAPF();
|
|
switch (Opcode) {
|
|
default:
|
|
break;
|
|
case Instruction::FNeg:
|
|
return ConstantFP::get(C->getContext(), neg(CV));
|
|
}
|
|
} else if (auto *VTy = dyn_cast<VectorType>(C->getType())) {
|
|
// Fast path for splatted constants.
|
|
if (Constant *Splat = C->getSplatValue())
|
|
if (Constant *Elt = ConstantFoldUnaryInstruction(Opcode, Splat))
|
|
return ConstantVector::getSplat(VTy->getElementCount(), Elt);
|
|
|
|
if (auto *FVTy = dyn_cast<FixedVectorType>(VTy)) {
|
|
// Fold each element and create a vector constant from those constants.
|
|
Type *Ty = IntegerType::get(FVTy->getContext(), 32);
|
|
SmallVector<Constant *, 16> Result;
|
|
for (unsigned i = 0, e = FVTy->getNumElements(); i != e; ++i) {
|
|
Constant *ExtractIdx = ConstantInt::get(Ty, i);
|
|
Constant *Elt = ConstantExpr::getExtractElement(C, ExtractIdx);
|
|
Constant *Res = ConstantFoldUnaryInstruction(Opcode, Elt);
|
|
if (!Res)
|
|
return nullptr;
|
|
Result.push_back(Res);
|
|
}
|
|
|
|
return ConstantVector::get(Result);
|
|
}
|
|
}
|
|
|
|
// We don't know how to fold this.
|
|
return nullptr;
|
|
}
|
|
|
|
Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1,
|
|
Constant *C2) {
|
|
assert(Instruction::isBinaryOp(Opcode) && "Non-binary instruction detected");
|
|
|
|
// Simplify BinOps with their identity values first. They are no-ops and we
|
|
// can always return the other value, including undef or poison values.
|
|
if (Constant *Identity = ConstantExpr::getBinOpIdentity(
|
|
Opcode, C1->getType(), /*AllowRHSIdentity*/ false)) {
|
|
if (C1 == Identity)
|
|
return C2;
|
|
if (C2 == Identity)
|
|
return C1;
|
|
} else if (Constant *Identity = ConstantExpr::getBinOpIdentity(
|
|
Opcode, C1->getType(), /*AllowRHSIdentity*/ true)) {
|
|
if (C2 == Identity)
|
|
return C1;
|
|
}
|
|
|
|
// Binary operations propagate poison.
|
|
if (isa<PoisonValue>(C1) || isa<PoisonValue>(C2))
|
|
return PoisonValue::get(C1->getType());
|
|
|
|
// Handle scalar UndefValue and scalable vector UndefValue. Fixed-length
|
|
// vectors are always evaluated per element.
|
|
bool IsScalableVector = isa<ScalableVectorType>(C1->getType());
|
|
bool HasScalarUndefOrScalableVectorUndef =
|
|
(!C1->getType()->isVectorTy() || IsScalableVector) &&
|
|
(isa<UndefValue>(C1) || isa<UndefValue>(C2));
|
|
if (HasScalarUndefOrScalableVectorUndef) {
|
|
switch (static_cast<Instruction::BinaryOps>(Opcode)) {
|
|
case Instruction::Xor:
|
|
if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
|
|
// Handle undef ^ undef -> 0 special case. This is a common
|
|
// idiom (misuse).
|
|
return Constant::getNullValue(C1->getType());
|
|
[[fallthrough]];
|
|
case Instruction::Add:
|
|
case Instruction::Sub:
|
|
return UndefValue::get(C1->getType());
|
|
case Instruction::And:
|
|
if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef
|
|
return C1;
|
|
return Constant::getNullValue(C1->getType()); // undef & X -> 0
|
|
case Instruction::Mul: {
|
|
// undef * undef -> undef
|
|
if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
|
|
return C1;
|
|
const APInt *CV;
|
|
// X * undef -> undef if X is odd
|
|
if (match(C1, m_APInt(CV)) || match(C2, m_APInt(CV)))
|
|
if ((*CV)[0])
|
|
return UndefValue::get(C1->getType());
|
|
|
|
// X * undef -> 0 otherwise
|
|
return Constant::getNullValue(C1->getType());
|
|
}
|
|
case Instruction::SDiv:
|
|
case Instruction::UDiv:
|
|
// X / undef -> poison
|
|
// X / 0 -> poison
|
|
if (match(C2, m_CombineOr(m_Undef(), m_Zero())))
|
|
return PoisonValue::get(C2->getType());
|
|
// undef / X -> 0 otherwise
|
|
return Constant::getNullValue(C1->getType());
|
|
case Instruction::URem:
|
|
case Instruction::SRem:
|
|
// X % undef -> poison
|
|
// X % 0 -> poison
|
|
if (match(C2, m_CombineOr(m_Undef(), m_Zero())))
|
|
return PoisonValue::get(C2->getType());
|
|
// undef % X -> 0 otherwise
|
|
return Constant::getNullValue(C1->getType());
|
|
case Instruction::Or: // X | undef -> -1
|
|
if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef
|
|
return C1;
|
|
return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0
|
|
case Instruction::LShr:
|
|
// X >>l undef -> poison
|
|
if (isa<UndefValue>(C2))
|
|
return PoisonValue::get(C2->getType());
|
|
// undef >>l X -> 0
|
|
return Constant::getNullValue(C1->getType());
|
|
case Instruction::AShr:
|
|
// X >>a undef -> poison
|
|
if (isa<UndefValue>(C2))
|
|
return PoisonValue::get(C2->getType());
|
|
// TODO: undef >>a X -> poison if the shift is exact
|
|
// undef >>a X -> 0
|
|
return Constant::getNullValue(C1->getType());
|
|
case Instruction::Shl:
|
|
// X << undef -> undef
|
|
if (isa<UndefValue>(C2))
|
|
return PoisonValue::get(C2->getType());
|
|
// undef << X -> 0
|
|
return Constant::getNullValue(C1->getType());
|
|
case Instruction::FSub:
|
|
// -0.0 - undef --> undef (consistent with "fneg undef")
|
|
if (match(C1, m_NegZeroFP()) && isa<UndefValue>(C2))
|
|
return C2;
|
|
[[fallthrough]];
|
|
case Instruction::FAdd:
|
|
case Instruction::FMul:
|
|
case Instruction::FDiv:
|
|
case Instruction::FRem:
|
|
// [any flop] undef, undef -> undef
|
|
if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
|
|
return C1;
|
|
// [any flop] C, undef -> NaN
|
|
// [any flop] undef, C -> NaN
|
|
// We could potentially specialize NaN/Inf constants vs. 'normal'
|
|
// constants (possibly differently depending on opcode and operand). This
|
|
// would allow returning undef sometimes. But it is always safe to fold to
|
|
// NaN because we can choose the undef operand as NaN, and any FP opcode
|
|
// with a NaN operand will propagate NaN.
|
|
return ConstantFP::getNaN(C1->getType());
|
|
case Instruction::BinaryOpsEnd:
|
|
llvm_unreachable("Invalid BinaryOp");
|
|
}
|
|
}
|
|
|
|
// Neither constant should be UndefValue, unless these are vector constants.
|
|
assert((!HasScalarUndefOrScalableVectorUndef) && "Unexpected UndefValue");
|
|
|
|
// Handle simplifications when the RHS is a constant int.
|
|
if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
|
|
if (C2 == ConstantExpr::getBinOpAbsorber(Opcode, C2->getType(),
|
|
/*AllowLHSConstant*/ false))
|
|
return C2;
|
|
|
|
switch (Opcode) {
|
|
case Instruction::UDiv:
|
|
case Instruction::SDiv:
|
|
if (CI2->isZero())
|
|
return PoisonValue::get(CI2->getType()); // X / 0 == poison
|
|
break;
|
|
case Instruction::URem:
|
|
case Instruction::SRem:
|
|
if (CI2->isOne())
|
|
return Constant::getNullValue(CI2->getType()); // X % 1 == 0
|
|
if (CI2->isZero())
|
|
return PoisonValue::get(CI2->getType()); // X % 0 == poison
|
|
break;
|
|
case Instruction::And:
|
|
assert(!CI2->isZero() && "And zero handled above");
|
|
if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
|
|
// If and'ing the address of a global with a constant, fold it.
|
|
if (CE1->getOpcode() == Instruction::PtrToInt &&
|
|
isa<GlobalValue>(CE1->getOperand(0))) {
|
|
GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0));
|
|
|
|
Align GVAlign; // defaults to 1
|
|
|
|
if (Module *TheModule = GV->getParent()) {
|
|
const DataLayout &DL = TheModule->getDataLayout();
|
|
GVAlign = GV->getPointerAlignment(DL);
|
|
|
|
// If the function alignment is not specified then assume that it
|
|
// is 4.
|
|
// This is dangerous; on x86, the alignment of the pointer
|
|
// corresponds to the alignment of the function, but might be less
|
|
// than 4 if it isn't explicitly specified.
|
|
// However, a fix for this behaviour was reverted because it
|
|
// increased code size (see https://reviews.llvm.org/D55115)
|
|
// FIXME: This code should be deleted once existing targets have
|
|
// appropriate defaults
|
|
if (isa<Function>(GV) && !DL.getFunctionPtrAlign())
|
|
GVAlign = Align(4);
|
|
} else if (isa<GlobalVariable>(GV)) {
|
|
GVAlign = cast<GlobalVariable>(GV)->getAlign().valueOrOne();
|
|
}
|
|
|
|
if (GVAlign > 1) {
|
|
unsigned DstWidth = CI2->getBitWidth();
|
|
unsigned SrcWidth = std::min(DstWidth, Log2(GVAlign));
|
|
APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth));
|
|
|
|
// If checking bits we know are clear, return zero.
|
|
if ((CI2->getValue() & BitsNotSet) == CI2->getValue())
|
|
return Constant::getNullValue(CI2->getType());
|
|
}
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
} else if (isa<ConstantInt>(C1)) {
|
|
// If C1 is a ConstantInt and C2 is not, swap the operands.
|
|
if (Instruction::isCommutative(Opcode))
|
|
return ConstantExpr::isDesirableBinOp(Opcode)
|
|
? ConstantExpr::get(Opcode, C2, C1)
|
|
: ConstantFoldBinaryInstruction(Opcode, C2, C1);
|
|
}
|
|
|
|
if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
|
|
if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
|
|
const APInt &C1V = CI1->getValue();
|
|
const APInt &C2V = CI2->getValue();
|
|
switch (Opcode) {
|
|
default:
|
|
break;
|
|
case Instruction::Add:
|
|
return ConstantInt::get(CI1->getContext(), C1V + C2V);
|
|
case Instruction::Sub:
|
|
return ConstantInt::get(CI1->getContext(), C1V - C2V);
|
|
case Instruction::Mul:
|
|
return ConstantInt::get(CI1->getContext(), C1V * C2V);
|
|
case Instruction::UDiv:
|
|
assert(!CI2->isZero() && "Div by zero handled above");
|
|
return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V));
|
|
case Instruction::SDiv:
|
|
assert(!CI2->isZero() && "Div by zero handled above");
|
|
if (C2V.isAllOnes() && C1V.isMinSignedValue())
|
|
return PoisonValue::get(CI1->getType()); // MIN_INT / -1 -> poison
|
|
return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V));
|
|
case Instruction::URem:
|
|
assert(!CI2->isZero() && "Div by zero handled above");
|
|
return ConstantInt::get(CI1->getContext(), C1V.urem(C2V));
|
|
case Instruction::SRem:
|
|
assert(!CI2->isZero() && "Div by zero handled above");
|
|
if (C2V.isAllOnes() && C1V.isMinSignedValue())
|
|
return PoisonValue::get(CI1->getType()); // MIN_INT % -1 -> poison
|
|
return ConstantInt::get(CI1->getContext(), C1V.srem(C2V));
|
|
case Instruction::And:
|
|
return ConstantInt::get(CI1->getContext(), C1V & C2V);
|
|
case Instruction::Or:
|
|
return ConstantInt::get(CI1->getContext(), C1V | C2V);
|
|
case Instruction::Xor:
|
|
return ConstantInt::get(CI1->getContext(), C1V ^ C2V);
|
|
case Instruction::Shl:
|
|
if (C2V.ult(C1V.getBitWidth()))
|
|
return ConstantInt::get(CI1->getContext(), C1V.shl(C2V));
|
|
return PoisonValue::get(C1->getType()); // too big shift is poison
|
|
case Instruction::LShr:
|
|
if (C2V.ult(C1V.getBitWidth()))
|
|
return ConstantInt::get(CI1->getContext(), C1V.lshr(C2V));
|
|
return PoisonValue::get(C1->getType()); // too big shift is poison
|
|
case Instruction::AShr:
|
|
if (C2V.ult(C1V.getBitWidth()))
|
|
return ConstantInt::get(CI1->getContext(), C1V.ashr(C2V));
|
|
return PoisonValue::get(C1->getType()); // too big shift is poison
|
|
}
|
|
}
|
|
|
|
if (C1 == ConstantExpr::getBinOpAbsorber(Opcode, C1->getType(),
|
|
/*AllowLHSConstant*/ true))
|
|
return C1;
|
|
} else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
|
|
if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
|
|
const APFloat &C1V = CFP1->getValueAPF();
|
|
const APFloat &C2V = CFP2->getValueAPF();
|
|
APFloat C3V = C1V; // copy for modification
|
|
switch (Opcode) {
|
|
default:
|
|
break;
|
|
case Instruction::FAdd:
|
|
(void)C3V.add(C2V, APFloat::rmNearestTiesToEven);
|
|
return ConstantFP::get(C1->getContext(), C3V);
|
|
case Instruction::FSub:
|
|
(void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven);
|
|
return ConstantFP::get(C1->getContext(), C3V);
|
|
case Instruction::FMul:
|
|
(void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven);
|
|
return ConstantFP::get(C1->getContext(), C3V);
|
|
case Instruction::FDiv:
|
|
(void)C3V.divide(C2V, APFloat::rmNearestTiesToEven);
|
|
return ConstantFP::get(C1->getContext(), C3V);
|
|
case Instruction::FRem:
|
|
(void)C3V.mod(C2V);
|
|
return ConstantFP::get(C1->getContext(), C3V);
|
|
}
|
|
}
|
|
} else if (auto *VTy = dyn_cast<VectorType>(C1->getType())) {
|
|
// Fast path for splatted constants.
|
|
if (Constant *C2Splat = C2->getSplatValue()) {
|
|
if (Instruction::isIntDivRem(Opcode) && C2Splat->isNullValue())
|
|
return PoisonValue::get(VTy);
|
|
if (Constant *C1Splat = C1->getSplatValue()) {
|
|
Constant *Res =
|
|
ConstantExpr::isDesirableBinOp(Opcode)
|
|
? ConstantExpr::get(Opcode, C1Splat, C2Splat)
|
|
: ConstantFoldBinaryInstruction(Opcode, C1Splat, C2Splat);
|
|
if (!Res)
|
|
return nullptr;
|
|
return ConstantVector::getSplat(VTy->getElementCount(), Res);
|
|
}
|
|
}
|
|
|
|
if (auto *FVTy = dyn_cast<FixedVectorType>(VTy)) {
|
|
// Fold each element and create a vector constant from those constants.
|
|
SmallVector<Constant*, 16> Result;
|
|
Type *Ty = IntegerType::get(FVTy->getContext(), 32);
|
|
for (unsigned i = 0, e = FVTy->getNumElements(); i != e; ++i) {
|
|
Constant *ExtractIdx = ConstantInt::get(Ty, i);
|
|
Constant *LHS = ConstantExpr::getExtractElement(C1, ExtractIdx);
|
|
Constant *RHS = ConstantExpr::getExtractElement(C2, ExtractIdx);
|
|
|
|
// If any element of a divisor vector is zero, the whole op is poison.
|
|
if (Instruction::isIntDivRem(Opcode) && RHS->isNullValue())
|
|
return PoisonValue::get(VTy);
|
|
|
|
Constant *Res = ConstantExpr::isDesirableBinOp(Opcode)
|
|
? ConstantExpr::get(Opcode, LHS, RHS)
|
|
: ConstantFoldBinaryInstruction(Opcode, LHS, RHS);
|
|
if (!Res)
|
|
return nullptr;
|
|
Result.push_back(Res);
|
|
}
|
|
|
|
return ConstantVector::get(Result);
|
|
}
|
|
}
|
|
|
|
if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
|
|
// There are many possible foldings we could do here. We should probably
|
|
// at least fold add of a pointer with an integer into the appropriate
|
|
// getelementptr. This will improve alias analysis a bit.
|
|
|
|
// Given ((a + b) + c), if (b + c) folds to something interesting, return
|
|
// (a + (b + c)).
|
|
if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) {
|
|
Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2);
|
|
if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode)
|
|
return ConstantExpr::get(Opcode, CE1->getOperand(0), T);
|
|
}
|
|
} else if (isa<ConstantExpr>(C2)) {
|
|
// If C2 is a constant expr and C1 isn't, flop them around and fold the
|
|
// other way if possible.
|
|
if (Instruction::isCommutative(Opcode))
|
|
return ConstantFoldBinaryInstruction(Opcode, C2, C1);
|
|
}
|
|
|
|
// i1 can be simplified in many cases.
|
|
if (C1->getType()->isIntegerTy(1)) {
|
|
switch (Opcode) {
|
|
case Instruction::Add:
|
|
case Instruction::Sub:
|
|
return ConstantExpr::getXor(C1, C2);
|
|
case Instruction::Shl:
|
|
case Instruction::LShr:
|
|
case Instruction::AShr:
|
|
// We can assume that C2 == 0. If it were one the result would be
|
|
// undefined because the shift value is as large as the bitwidth.
|
|
return C1;
|
|
case Instruction::SDiv:
|
|
case Instruction::UDiv:
|
|
// We can assume that C2 == 1. If it were zero the result would be
|
|
// undefined through division by zero.
|
|
return C1;
|
|
case Instruction::URem:
|
|
case Instruction::SRem:
|
|
// We can assume that C2 == 1. If it were zero the result would be
|
|
// undefined through division by zero.
|
|
return ConstantInt::getFalse(C1->getContext());
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
// We don't know how to fold this.
|
|
return nullptr;
|
|
}
|
|
|
|
static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1,
|
|
const GlobalValue *GV2) {
|
|
auto isGlobalUnsafeForEquality = [](const GlobalValue *GV) {
|
|
if (GV->isInterposable() || GV->hasGlobalUnnamedAddr())
|
|
return true;
|
|
if (const auto *GVar = dyn_cast<GlobalVariable>(GV)) {
|
|
Type *Ty = GVar->getValueType();
|
|
// A global with opaque type might end up being zero sized.
|
|
if (!Ty->isSized())
|
|
return true;
|
|
// A global with an empty type might lie at the address of any other
|
|
// global.
|
|
if (Ty->isEmptyTy())
|
|
return true;
|
|
}
|
|
return false;
|
|
};
|
|
// Don't try to decide equality of aliases.
|
|
if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2))
|
|
if (!isGlobalUnsafeForEquality(GV1) && !isGlobalUnsafeForEquality(GV2))
|
|
return ICmpInst::ICMP_NE;
|
|
return ICmpInst::BAD_ICMP_PREDICATE;
|
|
}
|
|
|
|
/// This function determines if there is anything we can decide about the two
|
|
/// constants provided. This doesn't need to handle simple things like integer
|
|
/// comparisons, but should instead handle ConstantExprs and GlobalValues.
|
|
/// If we can determine that the two constants have a particular relation to
|
|
/// each other, we should return the corresponding ICmp predicate, otherwise
|
|
/// return ICmpInst::BAD_ICMP_PREDICATE.
|
|
static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2) {
|
|
assert(V1->getType() == V2->getType() &&
|
|
"Cannot compare different types of values!");
|
|
if (V1 == V2) return ICmpInst::ICMP_EQ;
|
|
|
|
// The following folds only apply to pointers.
|
|
if (!V1->getType()->isPointerTy())
|
|
return ICmpInst::BAD_ICMP_PREDICATE;
|
|
|
|
// To simplify this code we canonicalize the relation so that the first
|
|
// operand is always the most "complex" of the two. We consider simple
|
|
// constants (like ConstantPointerNull) to be the simplest, followed by
|
|
// BlockAddress, GlobalValues, and ConstantExpr's (the most complex).
|
|
auto GetComplexity = [](Constant *V) {
|
|
if (isa<ConstantExpr>(V))
|
|
return 3;
|
|
if (isa<GlobalValue>(V))
|
|
return 2;
|
|
if (isa<BlockAddress>(V))
|
|
return 1;
|
|
return 0;
|
|
};
|
|
if (GetComplexity(V1) < GetComplexity(V2)) {
|
|
ICmpInst::Predicate SwappedRelation = evaluateICmpRelation(V2, V1);
|
|
if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE)
|
|
return ICmpInst::getSwappedPredicate(SwappedRelation);
|
|
return ICmpInst::BAD_ICMP_PREDICATE;
|
|
}
|
|
|
|
if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) {
|
|
// Now we know that the RHS is a BlockAddress or simple constant.
|
|
if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) {
|
|
// Block address in another function can't equal this one, but block
|
|
// addresses in the current function might be the same if blocks are
|
|
// empty.
|
|
if (BA2->getFunction() != BA->getFunction())
|
|
return ICmpInst::ICMP_NE;
|
|
} else if (isa<ConstantPointerNull>(V2)) {
|
|
return ICmpInst::ICMP_NE;
|
|
}
|
|
} else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) {
|
|
// Now we know that the RHS is a GlobalValue, BlockAddress or simple
|
|
// constant.
|
|
if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
|
|
return areGlobalsPotentiallyEqual(GV, GV2);
|
|
} else if (isa<BlockAddress>(V2)) {
|
|
return ICmpInst::ICMP_NE; // Globals never equal labels.
|
|
} else if (isa<ConstantPointerNull>(V2)) {
|
|
// GlobalVals can never be null unless they have external weak linkage.
|
|
// We don't try to evaluate aliases here.
|
|
// NOTE: We should not be doing this constant folding if null pointer
|
|
// is considered valid for the function. But currently there is no way to
|
|
// query it from the Constant type.
|
|
if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV) &&
|
|
!NullPointerIsDefined(nullptr /* F */,
|
|
GV->getType()->getAddressSpace()))
|
|
return ICmpInst::ICMP_UGT;
|
|
}
|
|
} else if (auto *CE1 = dyn_cast<ConstantExpr>(V1)) {
|
|
// Ok, the LHS is known to be a constantexpr. The RHS can be any of a
|
|
// constantexpr, a global, block address, or a simple constant.
|
|
Constant *CE1Op0 = CE1->getOperand(0);
|
|
|
|
switch (CE1->getOpcode()) {
|
|
case Instruction::GetElementPtr: {
|
|
GEPOperator *CE1GEP = cast<GEPOperator>(CE1);
|
|
// Ok, since this is a getelementptr, we know that the constant has a
|
|
// pointer type. Check the various cases.
|
|
if (isa<ConstantPointerNull>(V2)) {
|
|
// If we are comparing a GEP to a null pointer, check to see if the base
|
|
// of the GEP equals the null pointer.
|
|
if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
|
|
// If its not weak linkage, the GVal must have a non-zero address
|
|
// so the result is greater-than
|
|
if (!GV->hasExternalWeakLinkage() && CE1GEP->isInBounds())
|
|
return ICmpInst::ICMP_UGT;
|
|
}
|
|
} else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) {
|
|
if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) {
|
|
if (GV != GV2) {
|
|
if (CE1GEP->hasAllZeroIndices())
|
|
return areGlobalsPotentiallyEqual(GV, GV2);
|
|
return ICmpInst::BAD_ICMP_PREDICATE;
|
|
}
|
|
}
|
|
} else if (const auto *CE2GEP = dyn_cast<GEPOperator>(V2)) {
|
|
// By far the most common case to handle is when the base pointers are
|
|
// obviously to the same global.
|
|
const Constant *CE2Op0 = cast<Constant>(CE2GEP->getPointerOperand());
|
|
if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) {
|
|
// Don't know relative ordering, but check for inequality.
|
|
if (CE1Op0 != CE2Op0) {
|
|
if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices())
|
|
return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0),
|
|
cast<GlobalValue>(CE2Op0));
|
|
return ICmpInst::BAD_ICMP_PREDICATE;
|
|
}
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
return ICmpInst::BAD_ICMP_PREDICATE;
|
|
}
|
|
|
|
Constant *llvm::ConstantFoldCompareInstruction(CmpInst::Predicate Predicate,
|
|
Constant *C1, Constant *C2) {
|
|
Type *ResultTy;
|
|
if (VectorType *VT = dyn_cast<VectorType>(C1->getType()))
|
|
ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()),
|
|
VT->getElementCount());
|
|
else
|
|
ResultTy = Type::getInt1Ty(C1->getContext());
|
|
|
|
// Fold FCMP_FALSE/FCMP_TRUE unconditionally.
|
|
if (Predicate == FCmpInst::FCMP_FALSE)
|
|
return Constant::getNullValue(ResultTy);
|
|
|
|
if (Predicate == FCmpInst::FCMP_TRUE)
|
|
return Constant::getAllOnesValue(ResultTy);
|
|
|
|
// Handle some degenerate cases first
|
|
if (isa<PoisonValue>(C1) || isa<PoisonValue>(C2))
|
|
return PoisonValue::get(ResultTy);
|
|
|
|
if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
|
|
bool isIntegerPredicate = ICmpInst::isIntPredicate(Predicate);
|
|
// For EQ and NE, we can always pick a value for the undef to make the
|
|
// predicate pass or fail, so we can return undef.
|
|
// Also, if both operands are undef, we can return undef for int comparison.
|
|
if (ICmpInst::isEquality(Predicate) || (isIntegerPredicate && C1 == C2))
|
|
return UndefValue::get(ResultTy);
|
|
|
|
// Otherwise, for integer compare, pick the same value as the non-undef
|
|
// operand, and fold it to true or false.
|
|
if (isIntegerPredicate)
|
|
return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(Predicate));
|
|
|
|
// Choosing NaN for the undef will always make unordered comparison succeed
|
|
// and ordered comparison fails.
|
|
return ConstantInt::get(ResultTy, CmpInst::isUnordered(Predicate));
|
|
}
|
|
|
|
if (C2->isNullValue()) {
|
|
// The caller is expected to commute the operands if the constant expression
|
|
// is C2.
|
|
// C1 >= 0 --> true
|
|
if (Predicate == ICmpInst::ICMP_UGE)
|
|
return Constant::getAllOnesValue(ResultTy);
|
|
// C1 < 0 --> false
|
|
if (Predicate == ICmpInst::ICMP_ULT)
|
|
return Constant::getNullValue(ResultTy);
|
|
}
|
|
|
|
// If the comparison is a comparison between two i1's, simplify it.
|
|
if (C1->getType()->isIntegerTy(1)) {
|
|
switch (Predicate) {
|
|
case ICmpInst::ICMP_EQ:
|
|
if (isa<ConstantInt>(C2))
|
|
return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2));
|
|
return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2);
|
|
case ICmpInst::ICMP_NE:
|
|
return ConstantExpr::getXor(C1, C2);
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) {
|
|
const APInt &V1 = cast<ConstantInt>(C1)->getValue();
|
|
const APInt &V2 = cast<ConstantInt>(C2)->getValue();
|
|
return ConstantInt::get(ResultTy, ICmpInst::compare(V1, V2, Predicate));
|
|
} else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) {
|
|
const APFloat &C1V = cast<ConstantFP>(C1)->getValueAPF();
|
|
const APFloat &C2V = cast<ConstantFP>(C2)->getValueAPF();
|
|
return ConstantInt::get(ResultTy, FCmpInst::compare(C1V, C2V, Predicate));
|
|
} else if (auto *C1VTy = dyn_cast<VectorType>(C1->getType())) {
|
|
|
|
// Fast path for splatted constants.
|
|
if (Constant *C1Splat = C1->getSplatValue())
|
|
if (Constant *C2Splat = C2->getSplatValue())
|
|
if (Constant *Elt =
|
|
ConstantFoldCompareInstruction(Predicate, C1Splat, C2Splat))
|
|
return ConstantVector::getSplat(C1VTy->getElementCount(), Elt);
|
|
|
|
// Do not iterate on scalable vector. The number of elements is unknown at
|
|
// compile-time.
|
|
if (isa<ScalableVectorType>(C1VTy))
|
|
return nullptr;
|
|
|
|
// If we can constant fold the comparison of each element, constant fold
|
|
// the whole vector comparison.
|
|
SmallVector<Constant*, 4> ResElts;
|
|
Type *Ty = IntegerType::get(C1->getContext(), 32);
|
|
// Compare the elements, producing an i1 result or constant expr.
|
|
for (unsigned I = 0, E = C1VTy->getElementCount().getKnownMinValue();
|
|
I != E; ++I) {
|
|
Constant *C1E =
|
|
ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, I));
|
|
Constant *C2E =
|
|
ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, I));
|
|
Constant *Elt = ConstantFoldCompareInstruction(Predicate, C1E, C2E);
|
|
if (!Elt)
|
|
return nullptr;
|
|
|
|
ResElts.push_back(Elt);
|
|
}
|
|
|
|
return ConstantVector::get(ResElts);
|
|
}
|
|
|
|
if (C1->getType()->isFPOrFPVectorTy()) {
|
|
if (C1 == C2) {
|
|
// We know that C1 == C2 || isUnordered(C1, C2).
|
|
if (Predicate == FCmpInst::FCMP_ONE)
|
|
return ConstantInt::getFalse(ResultTy);
|
|
else if (Predicate == FCmpInst::FCMP_UEQ)
|
|
return ConstantInt::getTrue(ResultTy);
|
|
}
|
|
} else {
|
|
// Evaluate the relation between the two constants, per the predicate.
|
|
int Result = -1; // -1 = unknown, 0 = known false, 1 = known true.
|
|
switch (evaluateICmpRelation(C1, C2)) {
|
|
default: llvm_unreachable("Unknown relational!");
|
|
case ICmpInst::BAD_ICMP_PREDICATE:
|
|
break; // Couldn't determine anything about these constants.
|
|
case ICmpInst::ICMP_EQ: // We know the constants are equal!
|
|
// If we know the constants are equal, we can decide the result of this
|
|
// computation precisely.
|
|
Result = ICmpInst::isTrueWhenEqual(Predicate);
|
|
break;
|
|
case ICmpInst::ICMP_ULT:
|
|
switch (Predicate) {
|
|
case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE:
|
|
Result = 1; break;
|
|
case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE:
|
|
Result = 0; break;
|
|
default:
|
|
break;
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_SLT:
|
|
switch (Predicate) {
|
|
case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE:
|
|
Result = 1; break;
|
|
case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE:
|
|
Result = 0; break;
|
|
default:
|
|
break;
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_UGT:
|
|
switch (Predicate) {
|
|
case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE:
|
|
Result = 1; break;
|
|
case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE:
|
|
Result = 0; break;
|
|
default:
|
|
break;
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_SGT:
|
|
switch (Predicate) {
|
|
case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE:
|
|
Result = 1; break;
|
|
case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE:
|
|
Result = 0; break;
|
|
default:
|
|
break;
|
|
}
|
|
break;
|
|
case ICmpInst::ICMP_ULE:
|
|
if (Predicate == ICmpInst::ICMP_UGT)
|
|
Result = 0;
|
|
if (Predicate == ICmpInst::ICMP_ULT || Predicate == ICmpInst::ICMP_ULE)
|
|
Result = 1;
|
|
break;
|
|
case ICmpInst::ICMP_SLE:
|
|
if (Predicate == ICmpInst::ICMP_SGT)
|
|
Result = 0;
|
|
if (Predicate == ICmpInst::ICMP_SLT || Predicate == ICmpInst::ICMP_SLE)
|
|
Result = 1;
|
|
break;
|
|
case ICmpInst::ICMP_UGE:
|
|
if (Predicate == ICmpInst::ICMP_ULT)
|
|
Result = 0;
|
|
if (Predicate == ICmpInst::ICMP_UGT || Predicate == ICmpInst::ICMP_UGE)
|
|
Result = 1;
|
|
break;
|
|
case ICmpInst::ICMP_SGE:
|
|
if (Predicate == ICmpInst::ICMP_SLT)
|
|
Result = 0;
|
|
if (Predicate == ICmpInst::ICMP_SGT || Predicate == ICmpInst::ICMP_SGE)
|
|
Result = 1;
|
|
break;
|
|
case ICmpInst::ICMP_NE:
|
|
if (Predicate == ICmpInst::ICMP_EQ)
|
|
Result = 0;
|
|
if (Predicate == ICmpInst::ICMP_NE)
|
|
Result = 1;
|
|
break;
|
|
}
|
|
|
|
// If we evaluated the result, return it now.
|
|
if (Result != -1)
|
|
return ConstantInt::get(ResultTy, Result);
|
|
|
|
if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) ||
|
|
(C1->isNullValue() && !C2->isNullValue())) {
|
|
// If C2 is a constant expr and C1 isn't, flip them around and fold the
|
|
// other way if possible.
|
|
// Also, if C1 is null and C2 isn't, flip them around.
|
|
Predicate = ICmpInst::getSwappedPredicate(Predicate);
|
|
return ConstantFoldCompareInstruction(Predicate, C2, C1);
|
|
}
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
Constant *llvm::ConstantFoldGetElementPtr(Type *PointeeTy, Constant *C,
|
|
std::optional<ConstantRange> InRange,
|
|
ArrayRef<Value *> Idxs) {
|
|
if (Idxs.empty()) return C;
|
|
|
|
Type *GEPTy = GetElementPtrInst::getGEPReturnType(
|
|
C, ArrayRef((Value *const *)Idxs.data(), Idxs.size()));
|
|
|
|
if (isa<PoisonValue>(C))
|
|
return PoisonValue::get(GEPTy);
|
|
|
|
if (isa<UndefValue>(C))
|
|
return UndefValue::get(GEPTy);
|
|
|
|
auto IsNoOp = [&]() {
|
|
// Avoid losing inrange information.
|
|
if (InRange)
|
|
return false;
|
|
|
|
return all_of(Idxs, [](Value *Idx) {
|
|
Constant *IdxC = cast<Constant>(Idx);
|
|
return IdxC->isNullValue() || isa<UndefValue>(IdxC);
|
|
});
|
|
};
|
|
if (IsNoOp())
|
|
return GEPTy->isVectorTy() && !C->getType()->isVectorTy()
|
|
? ConstantVector::getSplat(
|
|
cast<VectorType>(GEPTy)->getElementCount(), C)
|
|
: C;
|
|
|
|
return nullptr;
|
|
}
|