Re-land: [Analysis] Ensure use of strict fp exceptions in ConstantFolding #137652
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…ding To perform constant folding in math operations, the implementation of the ConstantFolding Analysis relies on the use of the math functions from the host's libm. In particular, it relies on checking the value of errno and IEEE exceptions to determine when an operation is safe to be constant-folded. On some platforms, such as BSD or Darwin, math library functions don't set errno, so the ConstantFolding check depends only on the value of IEEE exceptions. As the FP exception behaviour is set to `ignore` by default, the compiler can perform optimisations that would get in the way of such checks being performed correctly. This patch sets the FP exception behaviour to `strict` when compiling the `ConstantFolding.cpp` source file, ensuring the value of IEEE exceptions can be reliably used by its implementation. This re-lands the changes from llvm#136139, but using the `-ftrapping-math` compile option instead of `-ffp-exception-behavior` for GCC support.
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@llvm/pr-subscribers-llvm-analysis Author: Lucas Duarte Prates (pratlucas) ChangesTo perform constant folding in math operations, the implementation of On some platforms, such as BSD or Darwin, math library functions don't This patch sets the FP exception behaviour to This re-lands the changes from #136139, but using the Full diff: https://github.com/llvm/llvm-project/pull/137652.diff 1 Files Affected:
diff --git a/llvm/lib/Analysis/CMakeLists.txt b/llvm/lib/Analysis/CMakeLists.txt
index fbf3b587d6bd2..a17a75e6fbcac 100644
--- a/llvm/lib/Analysis/CMakeLists.txt
+++ b/llvm/lib/Analysis/CMakeLists.txt
@@ -23,6 +23,17 @@ if (DEFINED LLVM_HAVE_TF_AOT OR LLVM_HAVE_TFLITE)
endif()
endif()
+# The implementation of ConstantFolding.cpp relies on the use of math functions
+# from the host. In particular, it relies on the detection of floating point
+# exceptions originating from such math functions to prevent invalid cases
+# from being constant folded. Therefore, we must ensure that fp exceptions are
+# handled correctly.
+if (MSVC)
+ set_source_files_properties(ConstantFolding.cpp PROPERTIES COMPILE_OPTIONS "/fp:except")
+elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
+ set_source_files_properties(ConstantFolding.cpp PROPERTIES COMPILE_OPTIONS "-ftrapping-math")
+endif()
+
add_llvm_component_library(LLVMAnalysis
AliasAnalysis.cpp
AliasAnalysisEvaluator.cpp
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/186/builds/8612 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/146/builds/2812 Here is the relevant piece of the build log for the reference |
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I've introduced the split lib `AnalysisFpExc`. Let me know if better solutions would be applicable.
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…ding (llvm#137652) To perform constant folding in math operations, the implementation of the ConstantFolding Analysis relies on the use of the math functions from the host's libm. In particular, it relies on checking the value of errno and IEEE exceptions to determine when an operation is safe to be constant-folded. On some platforms, such as BSD or Darwin, math library functions don't set errno, so the ConstantFolding check depends only on the value of IEEE exceptions. As the FP exception behaviour is set to `ignore` by default, the compiler can perform optimisations that would get in the way of such checks being performed correctly. This patch sets the FP exception behaviour to `strict` when compiling the `ConstantFolding.cpp` source file, ensuring the value of IEEE exceptions can be reliably used by its implementation. This re-lands the changes from llvm#136139, but using the `-ftrapping-math` compile option instead of `-ffp-exception-behavior` for GCC support.
IanWood1
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May 6, 2025
I've introduced the split lib `AnalysisFpExc`. Let me know if better solutions would be applicable.
IanWood1
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to IanWood1/llvm-project
that referenced
this pull request
May 6, 2025
…ding (llvm#137652) To perform constant folding in math operations, the implementation of the ConstantFolding Analysis relies on the use of the math functions from the host's libm. In particular, it relies on checking the value of errno and IEEE exceptions to determine when an operation is safe to be constant-folded. On some platforms, such as BSD or Darwin, math library functions don't set errno, so the ConstantFolding check depends only on the value of IEEE exceptions. As the FP exception behaviour is set to `ignore` by default, the compiler can perform optimisations that would get in the way of such checks being performed correctly. This patch sets the FP exception behaviour to `strict` when compiling the `ConstantFolding.cpp` source file, ensuring the value of IEEE exceptions can be reliably used by its implementation. This re-lands the changes from llvm#136139, but using the `-ftrapping-math` compile option instead of `-ffp-exception-behavior` for GCC support.
IanWood1
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May 6, 2025
I've introduced the split lib `AnalysisFpExc`. Let me know if better solutions would be applicable.
IanWood1
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to IanWood1/llvm-project
that referenced
this pull request
May 6, 2025
…ding (llvm#137652) To perform constant folding in math operations, the implementation of the ConstantFolding Analysis relies on the use of the math functions from the host's libm. In particular, it relies on checking the value of errno and IEEE exceptions to determine when an operation is safe to be constant-folded. On some platforms, such as BSD or Darwin, math library functions don't set errno, so the ConstantFolding check depends only on the value of IEEE exceptions. As the FP exception behaviour is set to `ignore` by default, the compiler can perform optimisations that would get in the way of such checks being performed correctly. This patch sets the FP exception behaviour to `strict` when compiling the `ConstantFolding.cpp` source file, ensuring the value of IEEE exceptions can be reliably used by its implementation. This re-lands the changes from llvm#136139, but using the `-ftrapping-math` compile option instead of `-ffp-exception-behavior` for GCC support.
IanWood1
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May 6, 2025
I've introduced the split lib `AnalysisFpExc`. Let me know if better solutions would be applicable.
GeorgeARM
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May 7, 2025
…ding (llvm#137652) To perform constant folding in math operations, the implementation of the ConstantFolding Analysis relies on the use of the math functions from the host's libm. In particular, it relies on checking the value of errno and IEEE exceptions to determine when an operation is safe to be constant-folded. On some platforms, such as BSD or Darwin, math library functions don't set errno, so the ConstantFolding check depends only on the value of IEEE exceptions. As the FP exception behaviour is set to `ignore` by default, the compiler can perform optimisations that would get in the way of such checks being performed correctly. This patch sets the FP exception behaviour to `strict` when compiling the `ConstantFolding.cpp` source file, ensuring the value of IEEE exceptions can be reliably used by its implementation. This re-lands the changes from llvm#136139, but using the `-ftrapping-math` compile option instead of `-ffp-exception-behavior` for GCC support.
GeorgeARM
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I've introduced the split lib `AnalysisFpExc`. Let me know if better solutions would be applicable.
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…ding (llvm#137652) To perform constant folding in math operations, the implementation of the ConstantFolding Analysis relies on the use of the math functions from the host's libm. In particular, it relies on checking the value of errno and IEEE exceptions to determine when an operation is safe to be constant-folded. On some platforms, such as BSD or Darwin, math library functions don't set errno, so the ConstantFolding check depends only on the value of IEEE exceptions. As the FP exception behaviour is set to `ignore` by default, the compiler can perform optimisations that would get in the way of such checks being performed correctly. This patch sets the FP exception behaviour to `strict` when compiling the `ConstantFolding.cpp` source file, ensuring the value of IEEE exceptions can be reliably used by its implementation. This re-lands the changes from llvm#136139, but using the `-ftrapping-math` compile option instead of `-ffp-exception-behavior` for GCC support.
Ankur-0429
pushed a commit
to Ankur-0429/llvm-project
that referenced
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May 9, 2025
I've introduced the split lib `AnalysisFpExc`. Let me know if better solutions would be applicable.
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To perform constant folding in math operations, the implementation of
the ConstantFolding Analysis relies on the use of the math functions
from the host's libm. In particular, it relies on checking the value of
errno and IEEE exceptions to determine when an operation is safe to be
constant-folded.
On some platforms, such as BSD or Darwin, math library functions don't
set errno, so the ConstantFolding check depends only on the value of
IEEE exceptions. As the FP exception behaviour is set to
ignorebydefault, the compiler can perform optimisations that would get in the
way of such checks being performed correctly.
This patch sets the FP exception behaviour to
strictwhen compilingthe
ConstantFolding.cppsource file, ensuring the value of IEEEexceptions can be reliably used by its implementation.
This re-lands the changes from #136139, but using the
-ftrapping-mathcompile option instead of
-ffp-exception-behaviorfor GCC support.