| Message ID | 000301cf3c4a$5328c120$f97a4360$@bolton@arm.com |
|---|---|
| State | New |
| Headers | show |
On Mon, 10 Mar 2014, Ian Bolton wrote:
> OK for trunk or stage 1?
OK for trunk with the ChangeLog entry fixed (it's in c-family/ChangeLog,
so no gcc/c-family/ in the entry itself, and the date should be in
yyyy-mm-dd format).
diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c index b7478f3..92ba481 100644 --- a/gcc/c-family/c-opts.c +++ b/gcc/c-family/c-opts.c @@ -834,7 +834,8 @@ c_common_post_options (const char **pfilename) if (flag_iso && !c_dialect_cxx () && (global_options_set.x_flag_fp_contract_mode - == (enum fp_contract_mode) 0)) + == (enum fp_contract_mode) 0) + && flag_unsafe_math_optimizations == 0) flag_fp_contract_mode = FP_CONTRACT_OFF; /* By default we use C99 inline semantics in GNU99 or C99 mode. C99
Hi, In common.opt, -ffp-contract=fast is set as the default for GCC. But then it gets disabled in c-family/c-opts.c if you are using ISO C (e.g. with -std=c99). The reason for this patch is that if you have also specified -funsafe-math-optimizations (or -Ofast or -ffast-math) then it is likely your preference to have -ffp-contract=fast on, so you can generate fused multiply adds (fma standard pattern). This patch works by blocking the override if you have -funsafe-math-optimizations (directly or indirectly), causing fused multiply add to be used in the places where we might hope to see it. (I had considered forcing -ffp-contract=fast on in opts.c if you have -funsafe-math-optimizations, but it is already on by default ... and it didn't work either! The problem is that it is forced off unless you have explicitly asked for -ffp-contract=fast at the command-line.) Standard regressions passed. OK for trunk or stage 1? Cheers, Ian 10-03-2014 Ian Bolton <ian.bolton@arm.com> * gcc/c-family/c-opts.c (c_common_post_options): Don't override -ffp-contract=fast if unsafe-math-optimizations is on.