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a48f58c97f
This adds a new vectorize predication loop hint: #pragma clang loop vectorize_predicate(enable) that can be used to indicate to the vectoriser that all (load/store) instructions should be predicated (masked). This allows, for example, folding of the remainder loop into the main loop. This patch will be followed up with D64916 and D65197. The former is a refactoring in the loopvectorizer and the groundwork to make tail loop folding a more general concept, and in the latter the actual tail loop folding transformation will be implemented. Differential Revision: https://reviews.llvm.org/D64744 llvm-svn: 366989
368 lines
14 KiB
C++
368 lines
14 KiB
C++
//===--- SemaStmtAttr.cpp - Statement Attribute Handling ------------------===//
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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 stmt-related attribute processing.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/Sema/SemaInternal.h"
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#include "clang/AST/ASTContext.h"
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#include "clang/Basic/SourceManager.h"
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#include "clang/Sema/DelayedDiagnostic.h"
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#include "clang/Sema/Lookup.h"
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#include "clang/Sema/ScopeInfo.h"
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#include "llvm/ADT/StringExtras.h"
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using namespace clang;
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using namespace sema;
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static Attr *handleFallThroughAttr(Sema &S, Stmt *St, const ParsedAttr &A,
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SourceRange Range) {
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FallThroughAttr Attr(A.getRange(), S.Context,
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A.getAttributeSpellingListIndex());
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if (!isa<NullStmt>(St)) {
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S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target)
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<< Attr.getSpelling() << St->getBeginLoc();
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if (isa<SwitchCase>(St)) {
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SourceLocation L = S.getLocForEndOfToken(Range.getEnd());
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S.Diag(L, diag::note_fallthrough_insert_semi_fixit)
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<< FixItHint::CreateInsertion(L, ";");
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}
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return nullptr;
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}
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auto *FnScope = S.getCurFunction();
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if (FnScope->SwitchStack.empty()) {
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S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_outside_switch);
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return nullptr;
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}
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// If this is spelled as the standard C++17 attribute, but not in C++17, warn
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// about using it as an extension.
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if (!S.getLangOpts().CPlusPlus17 && A.isCXX11Attribute() &&
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!A.getScopeName())
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S.Diag(A.getLoc(), diag::ext_cxx17_attr) << A.getName();
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FnScope->setHasFallthroughStmt();
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return ::new (S.Context) auto(Attr);
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}
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static Attr *handleSuppressAttr(Sema &S, Stmt *St, const ParsedAttr &A,
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SourceRange Range) {
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if (A.getNumArgs() < 1) {
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S.Diag(A.getLoc(), diag::err_attribute_too_few_arguments) << A << 1;
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return nullptr;
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}
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std::vector<StringRef> DiagnosticIdentifiers;
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for (unsigned I = 0, E = A.getNumArgs(); I != E; ++I) {
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StringRef RuleName;
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if (!S.checkStringLiteralArgumentAttr(A, I, RuleName, nullptr))
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return nullptr;
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// FIXME: Warn if the rule name is unknown. This is tricky because only
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// clang-tidy knows about available rules.
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DiagnosticIdentifiers.push_back(RuleName);
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}
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return ::new (S.Context) SuppressAttr(
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A.getRange(), S.Context, DiagnosticIdentifiers.data(),
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DiagnosticIdentifiers.size(), A.getAttributeSpellingListIndex());
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}
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static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const ParsedAttr &A,
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SourceRange) {
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IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0);
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IdentifierLoc *OptionLoc = A.getArgAsIdent(1);
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IdentifierLoc *StateLoc = A.getArgAsIdent(2);
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Expr *ValueExpr = A.getArgAsExpr(3);
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StringRef PragmaName =
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llvm::StringSwitch<StringRef>(PragmaNameLoc->Ident->getName())
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.Cases("unroll", "nounroll", "unroll_and_jam", "nounroll_and_jam",
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PragmaNameLoc->Ident->getName())
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.Default("clang loop");
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if (St->getStmtClass() != Stmt::DoStmtClass &&
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St->getStmtClass() != Stmt::ForStmtClass &&
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St->getStmtClass() != Stmt::CXXForRangeStmtClass &&
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St->getStmtClass() != Stmt::WhileStmtClass) {
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std::string Pragma = "#pragma " + std::string(PragmaName);
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S.Diag(St->getBeginLoc(), diag::err_pragma_loop_precedes_nonloop) << Pragma;
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return nullptr;
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}
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LoopHintAttr::Spelling Spelling =
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LoopHintAttr::Spelling(A.getAttributeSpellingListIndex());
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LoopHintAttr::OptionType Option;
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LoopHintAttr::LoopHintState State;
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auto SetHints = [&Option, &State](LoopHintAttr::OptionType O,
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LoopHintAttr::LoopHintState S) {
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Option = O;
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State = S;
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};
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if (PragmaName == "nounroll") {
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SetHints(LoopHintAttr::Unroll, LoopHintAttr::Disable);
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} else if (PragmaName == "unroll") {
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// #pragma unroll N
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if (ValueExpr)
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SetHints(LoopHintAttr::UnrollCount, LoopHintAttr::Numeric);
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else
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SetHints(LoopHintAttr::Unroll, LoopHintAttr::Enable);
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} else if (PragmaName == "nounroll_and_jam") {
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SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Disable);
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} else if (PragmaName == "unroll_and_jam") {
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// #pragma unroll_and_jam N
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if (ValueExpr)
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SetHints(LoopHintAttr::UnrollAndJamCount, LoopHintAttr::Numeric);
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else
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SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Enable);
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} else {
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// #pragma clang loop ...
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assert(OptionLoc && OptionLoc->Ident &&
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"Attribute must have valid option info.");
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Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
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OptionLoc->Ident->getName())
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.Case("vectorize", LoopHintAttr::Vectorize)
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.Case("vectorize_width", LoopHintAttr::VectorizeWidth)
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.Case("interleave", LoopHintAttr::Interleave)
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.Case("vectorize_predicate", LoopHintAttr::VectorizePredicate)
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.Case("interleave_count", LoopHintAttr::InterleaveCount)
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.Case("unroll", LoopHintAttr::Unroll)
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.Case("unroll_count", LoopHintAttr::UnrollCount)
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.Case("pipeline", LoopHintAttr::PipelineDisabled)
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.Case("pipeline_initiation_interval",
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LoopHintAttr::PipelineInitiationInterval)
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.Case("distribute", LoopHintAttr::Distribute)
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.Default(LoopHintAttr::Vectorize);
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if (Option == LoopHintAttr::VectorizeWidth ||
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Option == LoopHintAttr::InterleaveCount ||
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Option == LoopHintAttr::UnrollCount ||
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Option == LoopHintAttr::PipelineInitiationInterval) {
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assert(ValueExpr && "Attribute must have a valid value expression.");
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if (S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
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return nullptr;
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State = LoopHintAttr::Numeric;
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} else if (Option == LoopHintAttr::Vectorize ||
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Option == LoopHintAttr::Interleave ||
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Option == LoopHintAttr::VectorizePredicate ||
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Option == LoopHintAttr::Unroll ||
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Option == LoopHintAttr::Distribute ||
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Option == LoopHintAttr::PipelineDisabled) {
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assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument");
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if (StateLoc->Ident->isStr("disable"))
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State = LoopHintAttr::Disable;
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else if (StateLoc->Ident->isStr("assume_safety"))
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State = LoopHintAttr::AssumeSafety;
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else if (StateLoc->Ident->isStr("full"))
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State = LoopHintAttr::Full;
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else if (StateLoc->Ident->isStr("enable"))
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State = LoopHintAttr::Enable;
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else
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llvm_unreachable("bad loop hint argument");
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} else
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llvm_unreachable("bad loop hint");
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}
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return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, State,
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ValueExpr, A.getRange());
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}
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static void
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CheckForIncompatibleAttributes(Sema &S,
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const SmallVectorImpl<const Attr *> &Attrs) {
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// There are 6 categories of loop hints attributes: vectorize, interleave,
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// unroll, unroll_and_jam, pipeline and distribute. Except for distribute they
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// come in two variants: a state form and a numeric form. The state form
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// selectively defaults/enables/disables the transformation for the loop
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// (for unroll, default indicates full unrolling rather than enabling the
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// transformation). The numeric form form provides an integer hint (for
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// example, unroll count) to the transformer. The following array accumulates
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// the hints encountered while iterating through the attributes to check for
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// compatibility.
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struct {
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const LoopHintAttr *StateAttr;
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const LoopHintAttr *NumericAttr;
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} HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
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{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
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{nullptr, nullptr}};
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for (const auto *I : Attrs) {
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const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
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// Skip non loop hint attributes
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if (!LH)
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continue;
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LoopHintAttr::OptionType Option = LH->getOption();
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enum {
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Vectorize,
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Interleave,
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Unroll,
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UnrollAndJam,
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Distribute,
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Pipeline,
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VectorizePredicate
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} Category;
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switch (Option) {
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case LoopHintAttr::Vectorize:
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case LoopHintAttr::VectorizeWidth:
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Category = Vectorize;
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break;
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case LoopHintAttr::Interleave:
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case LoopHintAttr::InterleaveCount:
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Category = Interleave;
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break;
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case LoopHintAttr::Unroll:
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case LoopHintAttr::UnrollCount:
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Category = Unroll;
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break;
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case LoopHintAttr::UnrollAndJam:
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case LoopHintAttr::UnrollAndJamCount:
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Category = UnrollAndJam;
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break;
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case LoopHintAttr::Distribute:
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// Perform the check for duplicated 'distribute' hints.
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Category = Distribute;
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break;
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case LoopHintAttr::PipelineDisabled:
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case LoopHintAttr::PipelineInitiationInterval:
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Category = Pipeline;
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break;
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case LoopHintAttr::VectorizePredicate:
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Category = VectorizePredicate;
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break;
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};
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assert(Category < sizeof(HintAttrs) / sizeof(HintAttrs[0]));
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auto &CategoryState = HintAttrs[Category];
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const LoopHintAttr *PrevAttr;
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if (Option == LoopHintAttr::Vectorize ||
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Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll ||
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Option == LoopHintAttr::UnrollAndJam ||
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Option == LoopHintAttr::VectorizePredicate ||
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Option == LoopHintAttr::PipelineDisabled ||
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Option == LoopHintAttr::Distribute) {
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// Enable|Disable|AssumeSafety hint. For example, vectorize(enable).
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PrevAttr = CategoryState.StateAttr;
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CategoryState.StateAttr = LH;
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} else {
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// Numeric hint. For example, vectorize_width(8).
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PrevAttr = CategoryState.NumericAttr;
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CategoryState.NumericAttr = LH;
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}
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PrintingPolicy Policy(S.Context.getLangOpts());
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SourceLocation OptionLoc = LH->getRange().getBegin();
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if (PrevAttr)
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// Cannot specify same type of attribute twice.
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S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
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<< /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
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<< LH->getDiagnosticName(Policy);
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if (CategoryState.StateAttr && CategoryState.NumericAttr &&
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(Category == Unroll || Category == UnrollAndJam ||
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CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
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// Disable hints are not compatible with numeric hints of the same
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// category. As a special case, numeric unroll hints are also not
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// compatible with enable or full form of the unroll pragma because these
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// directives indicate full unrolling.
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S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
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<< /*Duplicate=*/false
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<< CategoryState.StateAttr->getDiagnosticName(Policy)
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<< CategoryState.NumericAttr->getDiagnosticName(Policy);
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}
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}
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}
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static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A,
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SourceRange Range) {
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// Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's
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// useful for OpenCL 1.x too and doesn't require HW support.
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// opencl_unroll_hint can have 0 arguments (compiler
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// determines unrolling factor) or 1 argument (the unroll factor provided
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// by the user).
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unsigned NumArgs = A.getNumArgs();
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if (NumArgs > 1) {
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S.Diag(A.getLoc(), diag::err_attribute_too_many_arguments) << A << 1;
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return nullptr;
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}
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unsigned UnrollFactor = 0;
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if (NumArgs == 1) {
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Expr *E = A.getArgAsExpr(0);
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llvm::APSInt ArgVal(32);
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if (!E->isIntegerConstantExpr(ArgVal, S.Context)) {
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S.Diag(A.getLoc(), diag::err_attribute_argument_type)
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<< A << AANT_ArgumentIntegerConstant << E->getSourceRange();
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return nullptr;
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}
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int Val = ArgVal.getSExtValue();
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if (Val <= 0) {
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S.Diag(A.getRange().getBegin(),
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diag::err_attribute_requires_positive_integer)
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<< A << /* positive */ 0;
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return nullptr;
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}
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UnrollFactor = Val;
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}
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return OpenCLUnrollHintAttr::CreateImplicit(S.Context, UnrollFactor);
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}
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static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A,
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SourceRange Range) {
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switch (A.getKind()) {
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case ParsedAttr::UnknownAttribute:
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S.Diag(A.getLoc(), A.isDeclspecAttribute()
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? (unsigned)diag::warn_unhandled_ms_attribute_ignored
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: (unsigned)diag::warn_unknown_attribute_ignored)
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<< A.getName();
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return nullptr;
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case ParsedAttr::AT_FallThrough:
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return handleFallThroughAttr(S, St, A, Range);
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case ParsedAttr::AT_LoopHint:
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return handleLoopHintAttr(S, St, A, Range);
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case ParsedAttr::AT_OpenCLUnrollHint:
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return handleOpenCLUnrollHint(S, St, A, Range);
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case ParsedAttr::AT_Suppress:
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return handleSuppressAttr(S, St, A, Range);
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default:
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// if we're here, then we parsed a known attribute, but didn't recognize
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// it as a statement attribute => it is declaration attribute
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S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt)
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<< A.getName() << St->getBeginLoc();
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return nullptr;
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}
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}
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StmtResult Sema::ProcessStmtAttributes(Stmt *S,
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const ParsedAttributesView &AttrList,
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SourceRange Range) {
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SmallVector<const Attr*, 8> Attrs;
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for (const ParsedAttr &AL : AttrList) {
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if (Attr *a = ProcessStmtAttribute(*this, S, AL, Range))
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Attrs.push_back(a);
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}
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CheckForIncompatibleAttributes(*this, Attrs);
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if (Attrs.empty())
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return S;
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return ActOnAttributedStmt(Range.getBegin(), Attrs, S);
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}
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