[llvm] [SimplifyLibCalls] fdim constant fold (PR #109235)
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Mon Oct 7 23:01:59 PDT 2024
https://github.com/braw-lee updated https://github.com/llvm/llvm-project/pull/109235
>From 5d907ac436097b1d2719d3c6db6b74d1e993a6f4 Mon Sep 17 00:00:00 2001
From: Kushal Pal <kushalpal109 at gmail.com>
Date: Sun, 15 Sep 2024 17:19:38 +0530
Subject: [PATCH] [SimplifyLibCalls] Constant fold `fdim`
Signed-off-by: Kushal Pal <kushalpal109 at gmail.com>
---
.../llvm/Transforms/Utils/SimplifyLibCalls.h | 1 +
.../lib/Transforms/Utils/SimplifyLibCalls.cpp | 50 ++++++++
llvm/test/Transforms/InstCombine/fdim.ll | 121 ++++++++++++++++++
3 files changed, 172 insertions(+)
create mode 100644 llvm/test/Transforms/InstCombine/fdim.ll
diff --git a/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h b/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h
index 2d3d2ada6183a7..128502b99d9a37 100644
--- a/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h
+++ b/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h
@@ -212,6 +212,7 @@ class LibCallSimplifier {
Value *optimizeTrigInversionPairs(CallInst *CI, IRBuilderBase &B);
Value *optimizeSymmetric(CallInst *CI, LibFunc Func, IRBuilderBase &B);
Value *optimizeRemquo(CallInst *CI, IRBuilderBase &B);
+ Value *optimizeFdim(CallInst *CI, IRBuilderBase &B);
// Wrapper for all floating point library call optimizations
Value *optimizeFloatingPointLibCall(CallInst *CI, LibFunc Func,
IRBuilderBase &B);
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 6799d333fb2844..b2983b3b7f7013 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -3109,6 +3109,52 @@ Value *LibCallSimplifier::optimizeRemquo(CallInst *CI, IRBuilderBase &B) {
return ConstantFP::get(CI->getType(), Rem);
}
+/// Constant folds fdim
+Value *LibCallSimplifier::optimizeFdim(CallInst *CI, IRBuilderBase &B) {
+ // Cannot perform the fold unless the call has attribute memory(none)
+ if (!CI->doesNotAccessMemory())
+ return nullptr;
+
+ // propogate poison/undef if any
+ if (match(CI->getArgOperand(0), m_Undef()))
+ return CI->getArgOperand(0);
+ if (match(CI->getArgOperand(1), m_Undef()))
+ return CI->getArgOperand(1);
+
+ const APFloat *X, *Y;
+ // Check if both values are constants
+ if (!match(CI->getArgOperand(0), m_APFloat(X)) ||
+ !match(CI->getArgOperand(1), m_APFloat(Y)))
+ return nullptr;
+
+ // If either argument is NaN, NaN is returned
+ if (X->isNaN())
+ return ConstantFP::get(CI->getType(), X->makeQuiet());
+ if (Y->isNaN())
+ return ConstantFP::get(CI->getType(), Y->makeQuiet());
+
+ // if X - Y overflows, it will set the errno, so we avoid the fold
+ APFloat Difference = *X;
+ APFloat::opStatus Status =
+ Difference.subtract(*Y, RoundingMode::NearestTiesToEven);
+ switch (Status) {
+ case APFloat::opStatus::opOK:
+ case APFloat::opStatus::opInexact:
+ case APFloat::opStatus::opUnderflow:
+ break;
+ case APFloat::opStatus::opOverflow:
+ case APFloat::opStatus::opInvalidOp:
+ case APFloat::opStatus::opDivByZero:
+ return nullptr;
+ }
+ auto *FSubCall =
+ copyFlags(*CI, B.CreateFSub(CI->getOperand(0), CI->getOperand(1)));
+ auto *FMaxCall = copyFlags(
+ *CI, B.CreateBinaryIntrinsic(Intrinsic::maximum, FSubCall,
+ ConstantFP::getZero(CI->getType())));
+ return FMaxCall;
+}
+
//===----------------------------------------------------------------------===//
// Integer Library Call Optimizations
//===----------------------------------------------------------------------===//
@@ -4042,6 +4088,10 @@ Value *LibCallSimplifier::optimizeFloatingPointLibCall(CallInst *CI,
if (hasFloatVersion(M, CI->getCalledFunction()->getName()))
return optimizeBinaryDoubleFP(CI, Builder, TLI);
return nullptr;
+ case LibFunc_fdim:
+ case LibFunc_fdimf:
+ case LibFunc_fdiml:
+ return optimizeFdim(CI, Builder);
case LibFunc_fminf:
case LibFunc_fmin:
case LibFunc_fminl:
diff --git a/llvm/test/Transforms/InstCombine/fdim.ll b/llvm/test/Transforms/InstCombine/fdim.ll
new file mode 100644
index 00000000000000..609c7d6d2886f8
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/fdim.ll
@@ -0,0 +1,121 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+define double @fdim_double() {
+; CHECK-LABEL: define double @fdim_double() {
+; CHECK-NEXT: ret double 2.500000e+00
+;
+ %dim = call double @fdim(double 10.5, double 8.0)
+ ret double %dim
+}
+
+define double @fdim_double1() {
+; CHECK-LABEL: define double @fdim_double1() {
+; CHECK-NEXT: ret double 0.000000e+00
+;
+ %dim = call double @fdim(double 7.0, double 8.0)
+ ret double %dim
+}
+
+define float @fdim_float() {
+; CHECK-LABEL: define float @fdim_float() {
+; CHECK-NEXT: ret float 0.000000e+00
+;
+ %dim = call float @fdimf(float 1.500000e+00, float 8.0)
+ ret float %dim
+}
+
+define float @fdim_float1() {
+; CHECK-LABEL: define float @fdim_float1() {
+; CHECK-NEXT: ret float 2.000000e+00
+;
+ %dim = call float @fdimf(float 1.000000e+01, float 8.0)
+ ret float %dim
+}
+
+define double @fdim_poison1() {
+; CHECK-LABEL: define double @fdim_poison1() {
+; CHECK-NEXT: ret double poison
+;
+ %dim = call double @fdim(double poison, double 1.0)
+ ret double %dim
+}
+
+define double @fdim_poison2() {
+; CHECK-LABEL: define double @fdim_poison2() {
+; CHECK-NEXT: ret double poison
+;
+ %dim = call double @fdim(double 1.0, double poison)
+ ret double %dim
+}
+
+define double @fdim_poison3() {
+; CHECK-LABEL: define double @fdim_poison3() {
+; CHECK-NEXT: ret double poison
+;
+ %dim = call double @fdim(double poison, double poison)
+ ret double %dim
+}
+
+define double @fdim_undef1() {
+; CHECK-LABEL: define double @fdim_undef1() {
+; CHECK-NEXT: ret double undef
+;
+ %dim = call double @fdim(double undef, double 1.0)
+ ret double %dim
+}
+
+define double @fdim_undef2() {
+; CHECK-LABEL: define double @fdim_undef2() {
+; CHECK-NEXT: ret double undef
+;
+ %dim = call double @fdim(double 1.0, double undef)
+ ret double %dim
+}
+
+define double @fdim_undef3() {
+; CHECK-LABEL: define double @fdim_undef3() {
+; CHECK-NEXT: ret double undef
+;
+ %dim = call double @fdim(double undef, double undef)
+ ret double %dim
+}
+
+define double @fdim_inf_ninf(){
+; CHECK-LABEL: define double @fdim_inf_ninf() {
+; CHECK-NEXT: ret double 0x7FF0000000000000
+;
+ %dim = call double @fdim(double 0x7FF0000000000000, double 0x8000000000000000 )
+ ret double %dim
+}
+
+define double @fdim_inf(){
+; CHECK-LABEL: define double @fdim_inf() {
+; CHECK-NEXT: [[DIM:%.*]] = call double @fdim(double 0x7FF0000000000000, double 0x7FF0000000000000)
+; CHECK-NEXT: ret double [[DIM]]
+;
+ %dim = call double @fdim(double 0x7FF0000000000000, double 0x7FF0000000000000)
+ ret double %dim
+}
+
+define double @fdim_nzero(){
+; CHECK-LABEL: define double @fdim_nzero() {
+; CHECK-NEXT: ret double 0.000000e+00
+;
+ %dim = call double @fdim(double -0.0, double +0.0)
+ ret double %dim
+}
+
+define double @fdim_strictfp(){
+; CHECK-LABEL: define double @fdim_strictfp() {
+; CHECK-NEXT: [[DIM:%.*]] = call double @fdim(double 1.000000e+01, double 8.000000e+00) #[[ATTR2:[0-9]+]]
+; CHECK-NEXT: ret double [[DIM]]
+;
+ %dim = call double @fdim(double 10.0, double 8.0) strictfp
+ ret double %dim
+}
+
+declare double @fdim(double, double) #0
+declare float @fdimf(float, float) #0
+
+attributes #0 = { memory(none)}
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