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| author | Szabolcs Nagy <nsz@port70.net> | 2013-08-18 15:34:07 +0000 |
|---|---|---|
| committer | Szabolcs Nagy <nsz@port70.net> | 2013-08-18 16:27:21 +0000 |
| commit | d8764bf84022397ff9d22310f78fcd78d801e2bf (patch) | |
| tree | 289574d06451582fd67b5cde646cd6bfd368fa66 /src/fenv/x86_64/fenv.s | |
| parent | baba2630c9cf778b41e218dfa980fcfdbec808e6 (diff) | |
| download | musl-d8764bf84022397ff9d22310f78fcd78d801e2bf.tar.gz musl-d8764bf84022397ff9d22310f78fcd78d801e2bf.tar.xz musl-d8764bf84022397ff9d22310f78fcd78d801e2bf.zip | |
optimize x86 feclearexcept: only use save/restore x87 fenv if needed
the x87 exception summary (ES) and stack fault (SF) flags may be spuriously cleared by feclearexcept using the fnclex instruction, but these flags are not observable through libc hence maintaining their state is not critical.
Diffstat (limited to 'src/fenv/x86_64/fenv.s')
| -rw-r--r-- | src/fenv/x86_64/fenv.s | 26 |
1 files changed, 11 insertions, 15 deletions
diff --git a/src/fenv/x86_64/fenv.s b/src/fenv/x86_64/fenv.s index c48dade3..dda6b61a 100644 --- a/src/fenv/x86_64/fenv.s +++ b/src/fenv/x86_64/fenv.s @@ -1,25 +1,21 @@ .global feclearexcept .type feclearexcept,@function feclearexcept: + # maintain exceptions in the sse mxcsr, clear x87 exceptions mov %edi,%ecx + fnstsw %ax + test %eax,%ecx + jz 1f + fnclex +1: stmxcsr -8(%rsp) + and $0x3f,%eax + or %eax,-8(%rsp) + test %ecx,-8(%rsp) + jz 1f not %ecx - stmxcsr -8(%rsp) and %ecx,-8(%rsp) ldmxcsr -8(%rsp) - test $0x3f,%ecx - jnz 2f -1: fnclex - xor %eax,%eax - ret -2: fnstsw %ax - and %ecx,%eax - jz 1b - sub $32,%rsp - fnstenv (%rsp) - mov %al,4(%rsp) - fldenv (%rsp) - add $32,%rsp - xor %eax,%eax +1: xor %eax,%eax ret .global feraiseexcept |