[llvm] dbf3b5f - [InstCombine] fold more shuffles with FP<->Int cast operands

[Sanjay Patel via llvm-commits]

Author: Sanjay Patel
Date: 2022-05-17T14:25:11-04:00
New Revision: dbf3b5f114553e4d5a446cd9ef57e98a8d04354e

URL: https://github.com/llvm/llvm-project/commit/dbf3b5f114553e4d5a446cd9ef57e98a8d04354e
DIFF: https://github.com/llvm/llvm-project/commit/dbf3b5f114553e4d5a446cd9ef57e98a8d04354e.diff

LOG: [InstCombine] fold more shuffles with FP<->Int cast operands

shuffle (cast X), (cast Y), Mask --> cast (shuffle X, Y, Mask)

This extends the transform added with 0353c2c996c5.

If the casts are to a larger element type, the transform
reduces shuffle bit width, so that should be a win for
most codegen (if not, it can be inverted).

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
    llvm/test/Transforms/InstCombine/vec_shuffle.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index 1e8165526d85..c5bdfa43f749 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -2306,10 +2306,10 @@ static Instruction *foldCastShuffle(ShuffleVectorInst &Shuf,
   if (ShufTy != ShufOpTy)
     return nullptr;
 
-  // TODO: Allow element-size-changing casts?
+  // TODO: Allow element-size-decreasing casts (ex: fptosi float to i8)?
   assert(isa<FixedVectorType>(CastSrcTy) && isa<FixedVectorType>(ShufOpTy) &&
          "Expected fixed vector operands for casts and binary shuffle");
-  if (CastSrcTy->getPrimitiveSizeInBits() != ShufOpTy->getPrimitiveSizeInBits())
+  if (CastSrcTy->getPrimitiveSizeInBits() > ShufOpTy->getPrimitiveSizeInBits())
     return nullptr;
 
   // At least one of the operands must have only one use (the shuffle).

diff  --git a/llvm/test/Transforms/InstCombine/vec_shuffle.ll b/llvm/test/Transforms/InstCombine/vec_shuffle.ll
index 746966a2e13d..20dab18266d0 100644
--- a/llvm/test/Transforms/InstCombine/vec_shuffle.ll
+++ b/llvm/test/Transforms/InstCombine/vec_shuffle.ll
@@ -2079,9 +2079,8 @@ define <3 x i16> @fptoui_shuf_
diff erent_source_types(<3 x float> %x, <3 x half>
 
 define <4 x i32> @fptoui_shuf_widen_elts(<4 x half> %x, <4 x half> %y) {
 ; CHECK-LABEL: @fptoui_shuf_widen_elts(
-; CHECK-NEXT:    [[NX:%.*]] = fptosi <4 x half> [[X:%.*]] to <4 x i32>
-; CHECK-NEXT:    [[NY:%.*]] = fptosi <4 x half> [[Y:%.*]] to <4 x i32>
-; CHECK-NEXT:    [[R:%.*]] = shufflevector <4 x i32> [[NX]], <4 x i32> [[NY]], <4 x i32> <i32 0, i32 1, i32 4, i32 5>
+; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <4 x half> [[X:%.*]], <4 x half> [[Y:%.*]], <4 x i32> <i32 0, i32 1, i32 4, i32 5>
+; CHECK-NEXT:    [[R:%.*]] = fptosi <4 x half> [[TMP1]] to <4 x i32>
 ; CHECK-NEXT:    ret <4 x i32> [[R]]
 ;
   %nx = fptosi <4 x half> %x to <4 x i32>