[InstCombine][X86] Tweak generic expansion of PACKSS/PACKUS to shuffle then truncate. NFCI.
This has no effect on constant folding but will be useful when we expand non-saturating PACKSS/PACKUS intrinsics.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359191 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index d8bc459..221ad58 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -593,12 +593,7 @@
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 @@
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.
