[llvm] [InstCombine] Fix `frexp(frexp(x)) -> frexp(x)` fold (PR #138837)
Iris Shi via llvm-commits
llvm-commits at lists.llvm.org
Wed May 7 02:59:31 PDT 2025
https://github.com/el-ev updated https://github.com/llvm/llvm-project/pull/138837
>From c7afb92733c6b14d80961e7617affd6acf8a19d4 Mon Sep 17 00:00:00 2001
From: Iris Shi <0.0 at owo.li>
Date: Wed, 7 May 2025 17:32:31 +0800
Subject: [PATCH 1/2] [InstCombine] Fix `frexp(frexp(x)) -> frexp(x)` fold
---
llvm/lib/Analysis/InstructionSimplify.cpp | 9 ---------
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp | 12 ++++++++++++
.../{InstSimplify => InstCombine}/frexp.ll | 11 +++++++----
3 files changed, 19 insertions(+), 13 deletions(-)
rename llvm/test/Transforms/{InstSimplify => InstCombine}/frexp.ll (96%)
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 5a2943de9066e..85e3be9cc45c3 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -6377,15 +6377,6 @@ static Value *simplifyUnaryIntrinsic(Function *F, Value *Op0,
if (isSplatValue(Op0))
return Op0;
break;
- case Intrinsic::frexp: {
- // Frexp is idempotent with the added complication of the struct return.
- if (match(Op0, m_ExtractValue<0>(m_Value(X)))) {
- if (match(X, m_Intrinsic<Intrinsic::frexp>(m_Value())))
- return X;
- }
-
- break;
- }
default:
break;
}
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 3e78b20e41f0d..624c97cf39de3 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3799,6 +3799,18 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
}
break;
}
+ case Intrinsic::frexp: {
+ Value *X;
+ // Frexp is idempotent with the added complication of the struct return.
+ if (match(II->getArgOperand(0), m_ExtractValue<0>(m_Value(X)))) {
+ if (match(X, m_Intrinsic<Intrinsic::frexp>(m_Value()))) {
+ X = Builder.CreateInsertValue(
+ X, ConstantInt::get(II->getType()->getStructElementType(1), 0), 1);
+ return replaceInstUsesWith(*II, X);
+ }
+ }
+ break;
+ }
default: {
// Handle target specific intrinsics
std::optional<Instruction *> V = targetInstCombineIntrinsic(*II);
diff --git a/llvm/test/Transforms/InstSimplify/frexp.ll b/llvm/test/Transforms/InstCombine/frexp.ll
similarity index 96%
rename from llvm/test/Transforms/InstSimplify/frexp.ll
rename to llvm/test/Transforms/InstCombine/frexp.ll
index 34cfce92bac43..6541f0d77a093 100644
--- a/llvm/test/Transforms/InstSimplify/frexp.ll
+++ b/llvm/test/Transforms/InstCombine/frexp.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
-; RUN: opt -S -passes=instsimplify %s | FileCheck %s
+; RUN: opt -S -passes=instcombine %s | FileCheck %s
declare { float, i32 } @llvm.frexp.f32.i32(float)
declare { <2 x float>, <2 x i32> } @llvm.frexp.v2f32.v2i32(<2 x float>)
@@ -12,7 +12,8 @@ define { float, i32 } @frexp_frexp(float %x) {
; CHECK-LABEL: define { float, i32 } @frexp_frexp(
; CHECK-SAME: float [[X:%.*]]) {
; CHECK-NEXT: [[FREXP0:%.*]] = call { float, i32 } @llvm.frexp.f32.i32(float [[X]])
-; CHECK-NEXT: ret { float, i32 } [[FREXP0]]
+; CHECK-NEXT: [[FREXP1:%.*]] = insertvalue { float, i32 } [[FREXP0]], i32 0, 1
+; CHECK-NEXT: ret { float, i32 } [[FREXP1]]
;
%frexp0 = call { float, i32 } @llvm.frexp.f32.i32(float %x)
%frexp0.0 = extractvalue { float, i32 } %frexp0, 0
@@ -24,7 +25,8 @@ define { <2 x float>, <2 x i32> } @frexp_frexp_vector(<2 x float> %x) {
; CHECK-LABEL: define { <2 x float>, <2 x i32> } @frexp_frexp_vector(
; CHECK-SAME: <2 x float> [[X:%.*]]) {
; CHECK-NEXT: [[FREXP0:%.*]] = call { <2 x float>, <2 x i32> } @llvm.frexp.v2f32.v2i32(<2 x float> [[X]])
-; CHECK-NEXT: ret { <2 x float>, <2 x i32> } [[FREXP0]]
+; CHECK-NEXT: [[FREXP1:%.*]] = insertvalue { <2 x float>, <2 x i32> } [[FREXP0]], <2 x i32> zeroinitializer, 1
+; CHECK-NEXT: ret { <2 x float>, <2 x i32> } [[FREXP1]]
;
%frexp0 = call { <2 x float>, <2 x i32> } @llvm.frexp.v2f32.v2i32(<2 x float> %x)
%frexp0.0 = extractvalue { <2 x float>, <2 x i32> } %frexp0, 0
@@ -47,7 +49,8 @@ define { <vscale x 2 x float>, <vscale x 2 x i32> } @frexp_frexp_scalable_vector
; CHECK-LABEL: define { <vscale x 2 x float>, <vscale x 2 x i32> } @frexp_frexp_scalable_vector(
; CHECK-SAME: <vscale x 2 x float> [[X:%.*]]) {
; CHECK-NEXT: [[FREXP0:%.*]] = call { <vscale x 2 x float>, <vscale x 2 x i32> } @llvm.frexp.nxv2f32.nxv2i32(<vscale x 2 x float> [[X]])
-; CHECK-NEXT: ret { <vscale x 2 x float>, <vscale x 2 x i32> } [[FREXP0]]
+; CHECK-NEXT: [[FREXP1:%.*]] = insertvalue { <vscale x 2 x float>, <vscale x 2 x i32> } [[FREXP0]], <vscale x 2 x i32> zeroinitializer, 1
+; CHECK-NEXT: ret { <vscale x 2 x float>, <vscale x 2 x i32> } [[FREXP1]]
;
%frexp0 = call { <vscale x 2 x float>, <vscale x 2 x i32> } @llvm.frexp.nxv2f32.nxv2i32(<vscale x 2 x float> %x)
%frexp0.0 = extractvalue { <vscale x 2 x float>, <vscale x 2 x i32> } %frexp0, 0
>From 93fcdea390991e03db544a19dd242d18cdd509e9 Mon Sep 17 00:00:00 2001
From: Iris Shi <0.0 at owo.li>
Date: Wed, 7 May 2025 17:59:04 +0800
Subject: [PATCH 2/2] apply suggestions
---
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 624c97cf39de3..e571738d74ac3 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3801,11 +3801,14 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
}
case Intrinsic::frexp: {
Value *X;
- // Frexp is idempotent with the added complication of the struct return.
+ // The first result is idempotent with the added complication of the struct
+ // return, and the second result is zero because the value is already
+ // normalized.
if (match(II->getArgOperand(0), m_ExtractValue<0>(m_Value(X)))) {
if (match(X, m_Intrinsic<Intrinsic::frexp>(m_Value()))) {
X = Builder.CreateInsertValue(
- X, ConstantInt::get(II->getType()->getStructElementType(1), 0), 1);
+ X, Constant::getNullValue(II->getType()->getStructElementType(1)),
+ 1);
return replaceInstUsesWith(*II, X);
}
}
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