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[x86] simplify logic in lowerShuffleWithUndefHalf(); NFCI 

This seems unnecessarily complicated because we gave names to
opposite polarity bools and have code comments that don't really
line up with the logic. 

Step 1: remove UndefUpper and assert that it is the opposite of 
UndefLower after the initial early exit.

llvm-svn: 352217
This commit is contained in:
Sanjay Patel 2019-01-25 17:00:41 +00:00
parent ca95ee5e11
commit 0020f8bb23
1 changed files with 9 additions and 7 deletions
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16
llvm/lib/Target/X86/X86ISelLowering.cpp
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@ -14386,13 +14386,15 @@ static SDValue lowerShuffleWithUndefHalf(const SDLoc &DL, MVT VT, SDValue V1,
MVT HalfVT = MVT::getVectorVT(VT.getVectorElementType(), HalfNumElts);
bool UndefLower = isUndefLowerHalf(Mask);
bool UndefUpper = isUndefUpperHalf(Mask);
if (!UndefLower && !UndefUpper)
if (!UndefLower && !isUndefUpperHalf(Mask))
return SDValue();
assert((!UndefLower || !isUndefUpperHalf(Mask)) &&
"Completely undef shuffle mask should have been simplified already");
// Upper half is undef and lower half is whole upper subvector.
// e.g. vector_shuffle <4, 5, 6, 7, u, u, u, u> or <2, 3, u, u>
if (UndefUpper &&
if (!UndefLower &&
isSequentialOrUndefInRange(Mask, 0, HalfNumElts, HalfNumElts)) {
SDValue Hi = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, HalfVT, V1,
DAG.getIntPtrConstant(HalfNumElts, DL));
@ -14428,24 +14430,24 @@ static SDValue lowerShuffleWithUndefHalf(const SDLoc &DL, MVT VT, SDValue V1,
return SDValue();
// XXXXuuuu - don't extract both uppers, instead shuffle and then extract.
if (UndefUpper && NumUpperHalves == 2)
if (!UndefLower && NumUpperHalves == 2)
return SDValue();
// AVX2 - XXXXuuuu - always extract lowers.
if (Subtarget.hasAVX2() && !(UndefUpper && NumUpperHalves == 0)) {
if (Subtarget.hasAVX2() && (UndefLower || NumUpperHalves != 0)) {
// AVX2 supports efficient immediate 64-bit element cross-lane shuffles.
if (VT == MVT::v4f64 || VT == MVT::v4i64)
return SDValue();
// AVX2 supports variable 32-bit element cross-lane shuffles.
if (VT == MVT::v8f32 || VT == MVT::v8i32) {
// XXXXuuuu - don't extract lowers and uppers.
if (UndefUpper && NumLowerHalves != 0 && NumUpperHalves != 0)
if (!UndefLower && NumLowerHalves != 0 && NumUpperHalves != 0)
return SDValue();
}
}
// AVX512 - XXXXuuuu - always extract lowers.
if (VT.is512BitVector() && !(UndefUpper && NumUpperHalves == 0))
if (VT.is512BitVector() && (UndefLower || NumUpperHalves != 0))
return SDValue();
auto GetHalfVector = [&](int HalfIdx) {