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[X86] Add INSERT_SUBVECTOR to ComputeNumSignBits

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This adds support for calculating sign bits of insert_subvector. I based it on the computeKnownBits.

My motivating case is propagating sign bits information across basic blocks on AVX targets where concatenating using insert_subvector is common.

Differential Revision: https://reviews.llvm.org/D56283

llvm-svn: 350432
This commit is contained in:
Craig Topper 2019-01-04 20:50:59 +00:00
parent 6b3153ada0
commit cfeb1cf9af
2 changed files with 45 additions and 29 deletions
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36
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -3693,7 +3693,7 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, const APInt &DemandedElts,
}
return ComputeNumSignBits(Src, Depth + 1);
}
case ISD::CONCAT_VECTORS:
case ISD::CONCAT_VECTORS: {
// Determine the minimum number of sign bits across all demanded
// elts of the input vectors. Early out if the result is already 1.
Tmp = std::numeric_limits<unsigned>::max();
@ -3711,6 +3711,40 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, const APInt &DemandedElts,
assert(Tmp <= VTBits && "Failed to determine minimum sign bits");
return Tmp;
}
case ISD::INSERT_SUBVECTOR: {
// If we know the element index, demand any elements from the subvector and
// the remainder from the src its inserted into, otherwise demand them all.
SDValue Src = Op.getOperand(0);
SDValue Sub = Op.getOperand(1);
auto *SubIdx = dyn_cast<ConstantSDNode>(Op.getOperand(2));
unsigned NumSubElts = Sub.getValueType().getVectorNumElements();
if (SubIdx && SubIdx->getAPIntValue().ule(NumElts - NumSubElts)) {
Tmp = std::numeric_limits<unsigned>::max();
uint64_t Idx = SubIdx->getZExtValue();
APInt DemandedSubElts = DemandedElts.extractBits(NumSubElts, Idx);
if (!!DemandedSubElts) {
Tmp = ComputeNumSignBits(Sub, DemandedSubElts, Depth + 1);
if (Tmp == 1) return 1; // early-out
}
APInt SubMask = APInt::getBitsSet(NumElts, Idx, Idx + NumSubElts);
APInt DemandedSrcElts = DemandedElts & ~SubMask;
if (!!DemandedSrcElts) {
Tmp2 = ComputeNumSignBits(Src, DemandedSrcElts, Depth + 1);
Tmp = std::min(Tmp, Tmp2);
}
assert(Tmp <= VTBits && "Failed to determine minimum sign bits");
return Tmp;
}
// Not able to determine the index so just assume worst case.
Tmp = ComputeNumSignBits(Sub, Depth + 1);
if (Tmp == 1) return 1; // early-out
Tmp2 = ComputeNumSignBits(Src, Depth + 1);
Tmp = std::min(Tmp, Tmp2);
assert(Tmp <= VTBits && "Failed to determine minimum sign bits");
return Tmp;
}
}
// If we are looking at the loaded value of the SDNode.
if (Op.getResNo() == 0) {

38
llvm/test/CodeGen/X86/known-signbits-vector.ll
View File

@ -394,20 +394,11 @@ define void @cross_bb_signbits_insert_subvec(<32 x i8>* %ptr, <32 x i8> %x, <32
; X32-LABEL: cross_bb_signbits_insert_subvec:
; X32: # %bb.0:
; X32-NEXT: movl {{[0-9]+}}(%esp), %eax
; X32-NEXT: vextractf128 $1, %ymm0, %xmm3
; X32-NEXT: vpxor %xmm2, %xmm2, %xmm2
; X32-NEXT: vpcmpeqb %xmm2, %xmm3, %xmm3
; X32-NEXT: vpcmpeqb %xmm2, %xmm0, %xmm0
; X32-NEXT: vinsertf128 $1, %xmm3, %ymm0, %ymm0
; X32-NEXT: vextractf128 $1, %ymm0, %xmm3
; X32-NEXT: vpsllw $7, %xmm3, %xmm3
; X32-NEXT: vmovdqa {{.*#+}} xmm4 = [128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128]
; X32-NEXT: vpand %xmm4, %xmm3, %xmm3
; X32-NEXT: vpcmpgtb %xmm3, %xmm2, %xmm3
; X32-NEXT: vpsllw $7, %xmm0, %xmm0
; X32-NEXT: vpand %xmm4, %xmm0, %xmm0
; X32-NEXT: vpcmpgtb %xmm0, %xmm2, %xmm0
; X32-NEXT: vinsertf128 $1, %xmm3, %ymm0, %ymm0
; X32-NEXT: vextractf128 $1, %ymm0, %xmm2
; X32-NEXT: vpxor %xmm3, %xmm3, %xmm3
; X32-NEXT: vpcmpeqb %xmm3, %xmm2, %xmm2
; X32-NEXT: vpcmpeqb %xmm3, %xmm0, %xmm0
; X32-NEXT: vinsertf128 $1, %xmm2, %ymm0, %ymm0
; X32-NEXT: vandnps %ymm1, %ymm0, %ymm1
; X32-NEXT: vandps {{\.LCPI.*}}, %ymm0, %ymm0
; X32-NEXT: vorps %ymm1, %ymm0, %ymm0
@ -417,20 +408,11 @@ define void @cross_bb_signbits_insert_subvec(<32 x i8>* %ptr, <32 x i8> %x, <32
;
; X64-LABEL: cross_bb_signbits_insert_subvec:
; X64: # %bb.0:
; X64-NEXT: vextractf128 $1, %ymm0, %xmm3
; X64-NEXT: vpxor %xmm2, %xmm2, %xmm2
; X64-NEXT: vpcmpeqb %xmm2, %xmm3, %xmm3
; X64-NEXT: vpcmpeqb %xmm2, %xmm0, %xmm0
; X64-NEXT: vinsertf128 $1, %xmm3, %ymm0, %ymm0
; X64-NEXT: vextractf128 $1, %ymm0, %xmm3
; X64-NEXT: vpsllw $7, %xmm3, %xmm3
; X64-NEXT: vmovdqa {{.*#+}} xmm4 = [128,128,128,128,128,128,128,128,128,128,128,128,128,128,128,128]
; X64-NEXT: vpand %xmm4, %xmm3, %xmm3
; X64-NEXT: vpcmpgtb %xmm3, %xmm2, %xmm3
; X64-NEXT: vpsllw $7, %xmm0, %xmm0
; X64-NEXT: vpand %xmm4, %xmm0, %xmm0
; X64-NEXT: vpcmpgtb %xmm0, %xmm2, %xmm0
; X64-NEXT: vinsertf128 $1, %xmm3, %ymm0, %ymm0
; X64-NEXT: vextractf128 $1, %ymm0, %xmm2
; X64-NEXT: vpxor %xmm3, %xmm3, %xmm3
; X64-NEXT: vpcmpeqb %xmm3, %xmm2, %xmm2
; X64-NEXT: vpcmpeqb %xmm3, %xmm0, %xmm0
; X64-NEXT: vinsertf128 $1, %xmm2, %ymm0, %ymm0
; X64-NEXT: vandnps %ymm1, %ymm0, %ymm1
; X64-NEXT: vandps {{.*}}(%rip), %ymm0, %ymm0
; X64-NEXT: vorps %ymm1, %ymm0, %ymm0