http://llvm.org/bugs/show_bug.cgi?id=17188
Bug ID: 17188
Summary: x86 FMA not generated unless fast-math is used?
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Backend: X86
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
I was expecting a target that has the FMA feature to use FMA instructions with
-O3 (or even less), but:
$ ./clang -v
clang version 3.4 (trunk 189776)
Target: x86_64-apple-darwin11.4.2
Thread model: posix
$ cat fma.c
double foo(double x) {
return x*x + x;
}
$ ./clang -S -O3 -fomit-frame-pointer -march=core-avx2 -o /dev/stdout fma.c
.section __TEXT,__text,regular,pure_instructions
.globl _foo
.align 4, 0x90
_foo: ## @foo
.cfi_startproc
## BB#0: ## %entry
vmulsd %xmm0, %xmm0, %xmm1
vaddsd %xmm0, %xmm1, %xmm0
ret
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