[llvm-dev] Weird behavior in LLVM regarding _finite math (original) (raw)
Jinsong Ji via llvm-dev llvm-dev at lists.llvm.org
Mon Jul 20 11:47:14 PDT 2020
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Hi Masoud:
This is because the math.h in your system still has FINITE_MATH_ONLY support.
-Ofast in clang will set macro __FINITE_MATH_ONLY__ to 1, so it will
preprocess your code,
and go into finite math path, which will do the renaming using __asm.
extern double log (double) asm ("" "__log_finite") attribute ((nothrow ));
This is expected. If you don't want it, you can use -fno-finite-math-only..
Or you can use newer version of glibc (hence no finite path in math.h at all).
Best,
Jinsong Ji (纪金松), PhD.
XL/LLVM on Power Compiler Development E-mail: jji at us.ibm.com
From: Masoud Ataei via llvm-dev <llvm-dev at lists.llvm.org> To: llvm-dev <llvm-dev at lists.llvm.org> Date: 07/20/2020 02:09 PM Subject: [EXTERNAL] [llvm-dev] Weird behavior in LLVM regarding _finite math Sent by: "llvm-dev" <llvm-dev-bounces at lists.llvm.org>
Hi,
It seems _finite math is gone for LLVM right now (
https://reviews.llvm.org/D74712) but there are still trace of it here:
$ cat a1.c
#include <math.h>
double log(double x){
return x;
}
$ cat a2.c
#include <math.h>
double mylog(double x){
return log(x);
}
Let compile both with -Ofast. We won't see __log_finite in the a2.s but
we will see the function name in a1.s is changed to __log_finite. Is it
expected?
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