> -----Original Message-----
> From: Robert Suchanek [mailto:[email protected]]
> Sent: Friday, September 04, 2015 10:21 AM
> To: Matthew Fortune; Richard Sandiford
> Cc: Moore, Catherine; [email protected]
> Subject: RE: [PATCH] Disable -mbranch-likely for -Os when targetting generic
> architecture
>
> Hi,
>
> > Richard Sandiford <[email protected]> writes:
> > > Robert Suchanek <[email protected]> writes:
> > > > The patch below disables generation of the branch likely
> > > > instructions for -
> > Os
> > > > but only for generic architecture. The branch likely may result
> > > > in some code size reduction but the cost of running the code on R6
> > > > core is
> > significant.
> > >
> > > How about instead splitting PTF_AVOID_BRANCHLIKELY into
> > > PTF_AVOID_BRANCHLIKELY_SPEED and
> PTF_AVOID_BRANCHLIKELY_SIZE?
> > > We could have PTF_AVOID_BRANCHLIKELY_ALWAYS as an OR of the two.
> >
> > This sounds OK and is nicer.
> >
> > > Anything that does string ops on the architecture is suspicious :-)
> >
> > You can blame me for this. I advocated the string comparison approach
> > as I had to do the same thing in gas IIRC for some feature and
> > couldn't think of anything better to suggest.
>
> Here is an updated version that use the suggested method. Ok to apply?
>
> Regards,
> Robert
>
> gcc/
> * config/mips/mips-cpus.def: Replace PTF_AVOID_BRANCHLIKELY
> with
> PTF_AVOID_BRANCHLIKELY_ALWAYS for generic architecture and
> with
> PTF_AVOID_BRANCHLIKELY_SPEED for others.
> (mips2, mips3, mips4): Add PTF_AVOID_BRANCHLIKELY_SIZE to tune
> flags.
> * config/mips/mips.c (mips_option_override): Enable the branch
> likely
> depending on the tune flags and optimization level.
> * config/mips/mips.h (PTF_AVOID_BRANCHLIKELY): Remove.
> (PTF_AVOID_BRANCHLIKELY_SPEED): Define.
> (PTF_AVOID_BRANCHLIKELY_SIZE): Likewise.
> (PTF_AVOID_BRANCHLIKELY_ALWAYS): Likewise.
> ---
> gcc/config/mips/mips-cpus.def | 56 +++++++++++++++++++++---------------
> -------
> gcc/config/mips/mips.c | 6 +++--
> gcc/config/mips/mips.h | 20 ++++++++++++----
> 3 files changed, 47 insertions(+), 35 deletions(-)
>
> a/gcc/config/mips/mips.c b/gcc/config/mips/mips.c index 0e0ecf2..f8775c4
> 100644
> --- a/gcc/config/mips/mips.c
> +++ b/gcc/config/mips/mips.c
> @@ -17916,8 +17916,10 @@ mips_option_override (void)
> if ((target_flags_explicit & MASK_BRANCHLIKELY) == 0)
> {
> if (ISA_HAS_BRANCHLIKELY
> - && (optimize_size
> - || (mips_tune_info->tune_flags & PTF_AVOID_BRANCHLIKELY)
> == 0))
> + && ((optimize_size && (mips_tune_info->tune_flags
> + & PTF_AVOID_BRANCHLIKELY_SIZE) == 0)
> + || (!optimize_size && (mips_tune_info->tune_flags
> + & PTF_AVOID_BRANCHLIKELY_SPEED) ==
> 0)))
> target_flags |= MASK_BRANCHLIKELY;
> else
> target_flags &= ~MASK_BRANCHLIKELY;
Should this check be:
Index: mips.c
===================================================================
--- mips.c (revision 229138)
+++ mips.c (working copy)
@@ -17758,8 +17758,15 @@
if ((target_flags_explicit & MASK_BRANCHLIKELY) == 0)
{
if (ISA_HAS_BRANCHLIKELY
- && (optimize_size
- || (mips_tune_info->tune_flags & PTF_AVOID_BRANCHLIKELY) == 0))
+ && ((optimize_size
+ && (mips_tune_info->tune_flags
+ & PTF_AVOID_BRANCHLIKELY_SIZE) == 0)
+ || (!optimize_size
+ && optimize > 0
+ && ((mips_tune_info->tune_flags
+ & PTF_AVOID_BRANCHLIKELY_SPEED) == 0))
+ || (mips_tune_info->tune_flags
+ & PTF_AVOID_BRANCHLIKELY_ALWAYS) == 0))
target_flags |= MASK_BRANCHLIKELY;
else
target_flags &= ~MASK_BRANCHLIKELY;
Instead? I don't see a use of PTF_AVOID_BRANCH_ALWAYS in your patch, but it
seems like it should be checked.
