[SimplifyLibCalls] Move constant folding logic in ConstantFoldLibCall2
#172139
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Moved constant folding logic from SimplifyLibCalls.cpp to ConstantFoldLibCall2
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@llvm/pr-subscribers-llvm-analysis @llvm/pr-subscribers-llvm-transforms Author: Ron Xavier (Ronxvier) ChangesMoved constant folding logic from SimplifyLibCalls.cpp to ConstantFoldLibCall2 Full diff: https://github.com/llvm/llvm-project/pull/172139.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index a9b51065a1d99..8a73c02bc363e 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -3241,6 +3241,18 @@ static Constant *ConstantFoldLibCall2(StringRef Name, Type *Ty,
if (TLI->has(Func))
return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
break;
+ case LibFunc_fdim:
+ case LibFunc_fdimf:
+ case LibFunc_fdiml:
+ if (TLI->has(Func)){
+ APFloat Difference = Op1V;
+ Difference.subtract(Op2V, RoundingMode::NearestTiesToEven);
+
+ APFloat MaxVal =
+ maximum(Difference, APFloat::getZero(Ty->getFltSemantics()));
+ return ConstantFP::get(Ty->getContext(), MaxVal);
+ }
+ break;
}
return nullptr;
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index c3537f544c432..55cd08b3de855 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -3201,18 +3201,8 @@ Value *LibCallSimplifier::optimizeFdim(CallInst *CI, IRBuilderBase &B) {
if (isa<PoisonValue>(CI->getArgOperand(1)))
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;
-
- APFloat Difference = *X;
- Difference.subtract(*Y, RoundingMode::NearestTiesToEven);
-
- APFloat MaxVal =
- maximum(Difference, APFloat::getZero(CI->getType()->getFltSemantics()));
- return ConstantFP::get(CI->getType(), MaxVal);
+ // Constant folding will be handled by ConstantFoldLibCall2
+ return nullptr;
}
//===----------------------------------------------------------------------===//
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You can test this locally with the following command:git-clang-format --diff origin/main HEAD --extensions cpp -- llvm/lib/Analysis/ConstantFolding.cpp llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp --diff_from_common_commit
View the diff from clang-format here.diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index dd4a3abf8..10e22b55c 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -3248,7 +3248,7 @@ static Constant *ConstantFoldLibCall2(StringRef Name, Type *Ty,
Difference.subtract(Op2V, RoundingMode::NearestTiesToEven);
APFloat MaxVal =
- maximum(Difference, APFloat::getZero(Ty->getFltSemantics()));
+ maximum(Difference, APFloat::getZero(Ty->getFltSemantics()));
return ConstantFP::get(Ty->getContext(), MaxVal);
break;
}
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🐧 Linux x64 Test Results
Failed Tests(click on a test name to see its output) LLVMLLVM.Transforms/InstCombine/fdim.llLLVM.Transforms/InstCombine/win-fdim.llIf these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the |
🪟 Windows x64 Test Results
Failed Tests(click on a test name to see its output) LLVMLLVM.Transforms/InstCombine/fdim.llLLVM.Transforms/InstCombine/win-fdim.llIf these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the |
Might be an overguarding issue
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antoniofrighetto
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antoniofrighetto
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We should introduce fdim names here too, to allow constant folding:
llvm-project/llvm/lib/Analysis/ConstantFolding.cpp
Lines 2002 to 2005 in 6a25e45
(I wonder if they should be intrinsics though)
antoniofrighetto
changed the title
ConstantFoldLibCall2
nikic
reviewed
Dec 15, 2025
| if (isa<PoisonValue>(CI->getArgOperand(0))) | ||
| return CI->getArgOperand(0); | ||
| if (isa<PoisonValue>(CI->getArgOperand(1))) | ||
| return CI->getArgOperand(1); |
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The poison cases shouldn't be in this file either.
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@nikic Sorry, I'm new to llvm contribution, do you mean poison cases should just be removed entirely? Because as I understand it, ConstantFoldLibCall2 only takes in operands of known constants
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Poison values are also constants. Though I don't think it matters since we always set noundef for operands passed to fdim: https://godbolt.org/z/9MhdToo6W
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Currently we cannot benefit from the vectorization of fdim (and other transformations except for constant folding). So it may be too early to turn it into intrinsics. |
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Point above still unresolved?
remove break that isn't reached Co-authored-by: Antonio Frighetto <me@antoniofrighetto.com>
arsenm
reviewed
Dec 16, 2025
Comment on lines
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| APFloat Difference = Op1V; | ||
| Difference.subtract(Op2V, RoundingMode::NearestTiesToEven); | ||
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||
| APFloat MaxVal = | ||
| maximum(Difference, APFloat::getZero(Ty->getFltSemantics())); |
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The actual implementation logic should probably be in APFloat
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Moved constant folding logic from SimplifyLibCalls.cpp to ConstantFoldLibCall2
Meant to resolve #171877