[llvm] [SLP]Add better minbitwidth analysis for udiv/urem instructions. (PR #85928)
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Wed Mar 20 06:34:30 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Alexey Bataev (alexey-bataev)
<details>
<summary>Changes</summary>
Adds improved bitwidth analysis for udiv/urem instructions. The
analysis is based on similar version in InstCombiner.
---
Full diff: https://github.com/llvm/llvm-project/pull/85928.diff
2 Files Affected:
- (modified) llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp (+22)
- (modified) llvm/test/Transforms/SLPVectorizer/X86/reorder-possible-strided-node.ll (+2-6)
``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 5d59f35f30810e..f8f7015e5f15f2 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -14165,6 +14165,28 @@ bool BoUpSLP::collectValuesToDemote(
return false;
break;
}
+ case Instruction::UDiv:
+ case Instruction::URem: {
+ if (ITE->UserTreeIndices.size() > 1 && !IsPotentiallyTruncated(I, BitWidth))
+ return false;
+ // UDiv and URem can be truncated if all the truncated bits are zero.
+ if (!AttemptCheckBitwidth(
+ [&](unsigned BitWidth, unsigned OrigBitWidth) {
+ assert(BitWidth <= OrigBitWidth && "Unexpected bitwidths!");
+ APInt Mask = APInt::getBitsSetFrom(OrigBitWidth, BitWidth);
+ return MaskedValueIsZero(I->getOperand(0), Mask,
+ SimplifyQuery(*DL)) &&
+ MaskedValueIsZero(I->getOperand(1), Mask,
+ SimplifyQuery(*DL));
+ },
+ NeedToExit))
+ return false;
+ if (NeedToExit)
+ return true;
+ if (!ProcessOperands({I->getOperand(0), I->getOperand(1)}, NeedToExit))
+ return false;
+ break;
+ }
// We can demote selects if we can demote their true and false values.
case Instruction::Select: {
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/reorder-possible-strided-node.ll b/llvm/test/Transforms/SLPVectorizer/X86/reorder-possible-strided-node.ll
index 4a23abf182e888..cfbbe14186b501 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/reorder-possible-strided-node.ll
+++ b/llvm/test/Transforms/SLPVectorizer/X86/reorder-possible-strided-node.ll
@@ -116,9 +116,7 @@ define void @test_div() {
; CHECK-NEXT: [[TMP1:%.*]] = load <4 x i32>, ptr [[ARRAYIDX22]], align 4
; CHECK-NEXT: [[TMP2:%.*]] = shufflevector <4 x i32> [[TMP1]], <4 x i32> poison, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
; CHECK-NEXT: [[TMP3:%.*]] = mul <4 x i32> [[TMP2]], [[TMP0]]
-; CHECK-NEXT: [[TMP4:%.*]] = zext <4 x i32> [[TMP3]] to <4 x i64>
-; CHECK-NEXT: [[TMP5:%.*]] = udiv <4 x i64> [[TMP4]], <i64 1, i64 2, i64 1, i64 2>
-; CHECK-NEXT: [[TMP6:%.*]] = trunc <4 x i64> [[TMP5]] to <4 x i32>
+; CHECK-NEXT: [[TMP6:%.*]] = udiv <4 x i32> [[TMP3]], <i32 1, i32 2, i32 1, i32 2>
; CHECK-NEXT: store <4 x i32> [[TMP6]], ptr getelementptr inbounds ([4 x i32], ptr null, i64 8, i64 0), align 16
; CHECK-NEXT: ret void
;
@@ -170,9 +168,7 @@ define void @test_rem() {
; CHECK-NEXT: [[TMP1:%.*]] = load <4 x i32>, ptr [[ARRAYIDX22]], align 4
; CHECK-NEXT: [[TMP2:%.*]] = shufflevector <4 x i32> [[TMP1]], <4 x i32> poison, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
; CHECK-NEXT: [[TMP3:%.*]] = mul <4 x i32> [[TMP2]], [[TMP0]]
-; CHECK-NEXT: [[TMP4:%.*]] = zext <4 x i32> [[TMP3]] to <4 x i64>
-; CHECK-NEXT: [[TMP5:%.*]] = urem <4 x i64> [[TMP4]], <i64 1, i64 2, i64 1, i64 1>
-; CHECK-NEXT: [[TMP6:%.*]] = trunc <4 x i64> [[TMP5]] to <4 x i32>
+; CHECK-NEXT: [[TMP6:%.*]] = urem <4 x i32> [[TMP3]], <i32 1, i32 2, i32 1, i32 1>
; CHECK-NEXT: store <4 x i32> [[TMP6]], ptr getelementptr inbounds ([4 x i32], ptr null, i64 8, i64 0), align 16
; CHECK-NEXT: ret void
;
``````````
</details>
https://github.com/llvm/llvm-project/pull/85928
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