[libc] Make LIBC_MATH_NO_ERRNO imply -fno-math-errno
#125794
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This partially reverts llvm#124200. Rather than using a CMake option to control whether to enable `-fno-math-errno`, use LIBC_MATH_NO_ERRNO configuration option. While there might be other cases when we want to set `-fno-math-errno`, having LIBC_MATH_NO_ERRNO imply it should be always safe and represents a reasonable starting point.
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@llvm/pr-subscribers-libc Author: Petr Hosek (petrhosek) ChangesThis partially reverts #124200. Rather than using a CMake option to control whether to enable Full diff: https://github.com/llvm/llvm-project/pull/125794.diff 3 Files Affected:
diff --git a/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake b/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake
index 0facb0b9be0c13..f5f638bef5c1d8 100644
--- a/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake
+++ b/libc/cmake/modules/LLVMLibCCompileOptionRules.cmake
@@ -28,13 +28,6 @@ function(_get_compile_options_from_flags output_var)
elseif(LIBC_TARGET_ARCHITECTURE_IS_RISCV64)
list(APPEND compile_options "-D__LIBC_RISCV_USE_FMA")
endif()
- # For clang, we will build the math functions with `-fno-math-errno` so that
- # __builtin_fma* will generate the fused-mutliply-add instructions. We
- # don't put the control flag to the public config yet, and see if it makes
- # sense to just enable this flag by default.
- if(LIBC_ADD_FNO_MATH_ERRNO)
- list(APPEND compile_options "-fno-math-errno")
- endif()
endif()
if(ADD_ROUND_OPT_FLAG)
if(LIBC_TARGET_ARCHITECTURE_IS_X86_64)
@@ -71,6 +64,9 @@ function(_get_compile_options_from_flags output_var)
"SHELL:-Xclang -target-feature -Xclang +fullfp16")
endif()
endif()
+ if(LIBC_CONF_MATH_OPTIMIZATIONS MATCHES "LIBC_MATH_NO_ERRNO")
+ list(APPEND compile_options "-fno-math-errno")
+ endif()
elseif(MSVC)
if(ADD_FMA_FLAG)
list(APPEND compile_options "/arch:AVX2")
diff --git a/libc/cmake/modules/LLVMLibCTestRules.cmake b/libc/cmake/modules/LLVMLibCTestRules.cmake
index 10bb9c9487d636..96fa6c3a707e47 100644
--- a/libc/cmake/modules/LLVMLibCTestRules.cmake
+++ b/libc/cmake/modules/LLVMLibCTestRules.cmake
@@ -1,11 +1,6 @@
function(_get_common_test_compile_options output_var c_test flags)
_get_compile_options_from_flags(compile_flags ${flags})
- # Remove -fno-math-errno if it was added.
- if(LIBC_ADD_FNO_MATH_ERRNO)
- list(REMOVE_ITEM compile_options "-fno-math-errno")
- endif()
-
set(compile_options
${LIBC_COMPILE_OPTIONS_DEFAULT}
${LIBC_TEST_COMPILE_OPTIONS_DEFAULT}
diff --git a/libc/config/baremetal/config.json b/libc/config/baremetal/config.json
index 08c581d1c68226..d29fb64e370ddb 100644
--- a/libc/config/baremetal/config.json
+++ b/libc/config/baremetal/config.json
@@ -28,7 +28,7 @@
},
"math": {
"LIBC_CONF_MATH_OPTIMIZATIONS": {
- "value": "(LIBC_MATH_SKIP_ACCURATE_PASS | LIBC_MATH_SMALL_TABLES)"
+ "value": "(LIBC_MATH_SKIP_ACCURATE_PASS | LIBC_MATH_SMALL_TABLES | LIBC_MATH_NO_ERRNO)"
}
}
}
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| "SHELL:-Xclang -target-feature -Xclang +fullfp16") | ||
| endif() | ||
| endif() | ||
| if(LIBC_CONF_MATH_OPTIMIZATIONS MATCHES "LIBC_MATH_NO_ERRNO") |
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Can you move this to L101-ish, where LIBC_CONF_MATH_OPTIMIZATIONS is checked?
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| # Remove -fno-math-errno if it was added. | ||
| if(LIBC_ADD_FNO_MATH_ERRNO) | ||
| list(REMOVE_ITEM compile_options "-fno-math-errno") |
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Are there tests failed because of this part? Last time I tried, there are failed math tests that check errno when the tests are built with -fno-math-errno.
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I don't see any test failures on the presubmit bots, should those exercise all tests?
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I mean the tests failed when the flag is set. I don't think any of our bots running baremetal config, so they don't cover this option.
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We don't currently run tests on baremetal so I don't know if we have any way to find out.
3 participants
This partially reverts #124200. Rather than using a CMake option to control whether to enable
-fno-math-errno, use LIBC_MATH_NO_ERRNO configuration option. While there might be other cases when we want to set-fno-math-errno, having LIBC_MATH_NO_ERRNO imply it should be always safe and represents a reasonable starting point.