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[InstCombine][X86] Tweak generic expansion of PACKSS/PACKUS to shuffle then truncate. NFCI.

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This has no effect on constant folding but will be useful when we expand non-saturating PACKSS/PACKUS intrinsics.

llvm-svn: 359191
This commit is contained in:
Simon Pilgrim 2019-04-25 13:51:57 +00:00
parent 0fc09d0d25
commit 48a3b54572
1 changed files with 4 additions and 7 deletions
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11
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
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@ -593,12 +593,7 @@ static Value *simplifyX86pack(IntrinsicInst &II,
Arg0 = Builder.CreateSelect(Builder.CreateICmpSGT(Arg0, MaxC), MaxC, Arg0);
Arg1 = Builder.CreateSelect(Builder.CreateICmpSGT(Arg1, MaxC), MaxC, Arg1);
// Truncate clamped args to dst size.
auto *TruncTy = VectorType::get(ResTy->getScalarType(), NumSrcElts);
Arg0 = Builder.CreateTrunc(Arg0, TruncTy);
Arg1 = Builder.CreateTrunc(Arg1, TruncTy);
// Shuffle args together at the lane level.
// Shuffle clamped args together at the lane level.
SmallVector<unsigned, 32> PackMask;
for (unsigned Lane = 0; Lane != NumLanes; ++Lane) {
for (unsigned Elt = 0; Elt != NumSrcEltsPerLane; ++Elt)
@ -606,8 +601,10 @@ static Value *simplifyX86pack(IntrinsicInst &II,
for (unsigned Elt = 0; Elt != NumSrcEltsPerLane; ++Elt)
PackMask.push_back(Elt + (Lane * NumSrcEltsPerLane) + NumSrcElts);
}
auto *Shuffle = Builder.CreateShuffleVector(Arg0, Arg1, PackMask);
return Builder.CreateShuffleVector(Arg0, Arg1, PackMask);
// Truncate to dst size.
return Builder.CreateTrunc(Shuffle, ResTy);
}
// Replace X86-specific intrinsics with generic floor-ceil where applicable.