[AArch64] Check for exact size when finding 1's for CMLE.

[davemgreen]

This is a fix for the second half of #75822, where smaller constants can also be bitcast to larger types. We should be checking the size is what we expect it to be when matching ones.

[llvmbot]

@llvm/pr-subscribers-backend-aarch64

Author: David Green (davemgreen)

Changes

This is a fix for the second half of #75822, where smaller constants can also be bitcast to larger types. We should be checking the size is what we expect it to be when matching ones.

---

Full diff: https://github.com/llvm/llvm-project/pull/76452.diff

2 Files Affected:

• (modified) llvm/lib/Target/AArch64/AArch64ISelLowering.cpp (+4-5)
• (modified) llvm/test/CodeGen/AArch64/neon-compare-instructions.ll (+2-1)

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index dffe69bdb900db..50658a855cfb37 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -13715,11 +13715,10 @@ static SDValue EmitVectorComparison(SDValue LHS, SDValue RHS,
   bool IsCnst = BVN && BVN->isConstantSplat(SplatValue, SplatUndef,
                                             SplatBitSize, HasAnyUndefs);
 
-  bool IsSplatUniform =
-      SrcVT.getVectorElementType().getSizeInBits() >= SplatBitSize;
-  bool IsZero = IsCnst && SplatValue == 0 && IsSplatUniform;
-  bool IsOne = IsCnst && SplatValue == 1 && IsSplatUniform;
-  bool IsMinusOne = IsCnst && SplatValue.isAllOnes() && IsSplatUniform;
+  bool IsZero = IsCnst && SplatValue == 0;
+  bool IsOne =
+      IsCnst && SrcVT.getScalarSizeInBits() == SplatBitSize && SplatValue == 1;
+  bool IsMinusOne = IsCnst && SplatValue.isAllOnes();
 
   if (SrcVT.getVectorElementType().isFloatingPoint()) {
     switch (CC) {
diff --git a/llvm/test/CodeGen/AArch64/neon-compare-instructions.ll b/llvm/test/CodeGen/AArch64/neon-compare-instructions.ll
index b2fc477d8655a4..3627c670429a03 100644
--- a/llvm/test/CodeGen/AArch64/neon-compare-instructions.ll
+++ b/llvm/test/CodeGen/AArch64/neon-compare-instructions.ll
@@ -1792,7 +1792,8 @@ define <8 x i1> @not_cmle8xi8(<8 x i8> %0) {
 define <4 x i1> @not_cmle16xi8(<4 x i32> %0) {
 ; CHECK-SD-LABEL: not_cmle16xi8:
 ; CHECK-SD:       // %bb.0: // %entry
-; CHECK-SD-NEXT:    cmle v0.4s, v0.4s, #0
+; CHECK-SD-NEXT:    movi v1.8h, #1
+; CHECK-SD-NEXT:    cmgt v0.4s, v1.4s, v0.4s
 ; CHECK-SD-NEXT:    xtn v0.4h, v0.4s
 ; CHECK-SD-NEXT:    ret
 ;

[antoniofrighetto]

Thank you for the patch, restricting the check to determine whether the splat matches the exact input size looks definitely more appropriate.

[davemgreen]

Cheers