[Float2Int] Make sure the CFP can be represented in the integer type#167699
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[Float2Int] Make sure the CFP can be represented in the integer type#167699
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@llvm/pr-subscribers-llvm-transforms Author: Yingwei Zheng (dtcxzyw) ChangesWhen Full diff: https://github.com/llvm/llvm-project/pull/167699.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Scalar/Float2Int.cpp b/llvm/lib/Transforms/Scalar/Float2Int.cpp
index 14686ce8c2ab6..37822cf05f144 100644
--- a/llvm/lib/Transforms/Scalar/Float2Int.cpp
+++ b/llvm/lib/Transforms/Scalar/Float2Int.cpp
@@ -237,10 +237,14 @@ std::optional<ConstantRange> Float2IntPass::calcRange(Instruction *I) {
// OK, it's representable. Now get it.
APSInt Int(MaxIntegerBW+1, false);
bool Exact;
- CF->getValueAPF().convertToInteger(Int,
- APFloat::rmNearestTiesToEven,
- &Exact);
- OpRanges.push_back(ConstantRange(Int));
+ APFloat::opStatus Status = CF->getValueAPF().convertToInteger(
+ Int, APFloat::rmNearestTiesToEven, &Exact);
+ // Although the round above is loseless, we still need to check if the
+ // floating-point value can be represented in the integer type.
+ if (Status == APFloat::opOK || Status == APFloat::opInexact)
+ OpRanges.push_back(ConstantRange(Int));
+ else
+ return badRange();
} else {
llvm_unreachable("Should have already marked this as badRange!");
}
diff --git a/llvm/test/Transforms/Float2Int/pr167627.ll b/llvm/test/Transforms/Float2Int/pr167627.ll
new file mode 100644
index 0000000000000..a170c21af7a2a
--- /dev/null
+++ b/llvm/test/Transforms/Float2Int/pr167627.ll
@@ -0,0 +1,18 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt -S -passes=float2int < %s | FileCheck %s
+
+; Make sure that we don't demote constant floating-point values when
+; it cannot be represented by target integer type.
+
+define i1 @pr167627() {
+; CHECK-LABEL: define i1 @pr167627() {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: [[FADD:%.*]] = fadd float 0xC5AAD8ABE0000000, 0xC57E819700000000
+; CHECK-NEXT: [[CMP:%.*]] = fcmp one float [[FADD]], 0.000000e+00
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+entry:
+ %fadd = fadd float 0xC5AAD8ABE0000000, 0xC57E819700000000
+ %cmp = fcmp one float %fadd, 0.000000e+00
+ ret i1 %cmp
+}
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antoniofrighetto
approved these changes
Nov 13, 2025
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antoniofrighetto
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Does make sense, thanks.
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/141/builds/12965 Here is the relevant piece of the build log for the reference |
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When
convertToIntegerfails, the integer result is undefined. In this case, we cannot use it in the subsequent steps.Close #167627.