mirror of
https://github.com/llvm/llvm-project.git
synced 2025-04-29 16:56:07 +00:00
cb8c009801
There are 2 parts to getting the -fassociative-math command-line flag translated to LLVM FMF:
1. In the driver/frontend, we accept the flag and its 'no' inverse and deal with the
interactions with other flags like -ffast-math -fno-signed-zeros -fno-trapping-math.
This was mostly already done - we just need to translate the flag as a codegen option.
The test file is complicated because there are many potential combinations of flags here.
Note that we are matching gcc's behavior that requires 'nsz' and no-trapping-math.
2. In codegen, we map the codegen option to FMF in the IR builder. This is simple code and
corresponding test.
For the motivating example from PR27372:
float foo(float a, float x) { return ((a + x) - x); }
$ ./clang -O2 27372.c -S -o - -ffast-math -fno-associative-math -emit-llvm | egrep 'fadd|fsub'
%add = fadd nnan ninf nsz arcp contract float %0, %1
%sub = fsub nnan ninf nsz arcp contract float %add, %2
So 'reassoc' is off as expected (and so is the new 'afn' but that's a different patch).
This case now works as expected end-to-end although the underlying logic is still wrong:
$ ./clang -O2 27372.c -S -o - -ffast-math -fno-associative-math | grep xmm
addss %xmm1, %xmm0
subss %xmm1, %xmm0
We're not done because the case where 'reassoc' is set is ignored by optimizer passes. Example:
$ ./clang -O2 27372.c -S -o - -fassociative-math -fno-signed-zeros -fno-trapping-math -emit-llvm | grep fadd
%add = fadd reassoc float %0, %1
$ ./clang -O2 27372.c -S -o - -fassociative-math -fno-signed-zeros -fno-trapping-math | grep xmm
addss %xmm1, %xmm0
subss %xmm1, %xmm0
Differential Revision: https://reviews.llvm.org/D39812
llvm-svn: 320920
20 lines
658 B
C
20 lines
658 B
C
// RUN: %clang_cc1 -ffinite-math-only -emit-llvm -o - %s | FileCheck %s -check-prefix=CHECK -check-prefix=FINITE
|
|
// RUN: %clang_cc1 -fno-signed-zeros -emit-llvm -o - %s | FileCheck %s -check-prefix=CHECK -check-prefix=NSZ
|
|
// RUN: %clang_cc1 -freciprocal-math -emit-llvm -o - %s | FileCheck %s -check-prefix=CHECK -check-prefix=RECIP
|
|
// RUN: %clang_cc1 -mreassociate -emit-llvm -o - %s | FileCheck %s -check-prefix=CHECK -check-prefix=REASSOC
|
|
|
|
float f0, f1, f2;
|
|
|
|
void foo(void) {
|
|
// CHECK-LABEL: define {{.*}}void @foo()
|
|
|
|
// FINITE: fadd nnan ninf
|
|
// NSZ: fadd nsz
|
|
// RECIP: fadd arcp
|
|
// REASSOC: fadd reassoc
|
|
f0 = f1 + f2;
|
|
|
|
// CHECK: ret
|
|
}
|
|
|