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Re: [0/3] Fix PR78120, in ifcvt/rtlanal/i386.
On Thu, Nov 24, 2016 at 10:14:24AM -0600, Segher Boessenkool wrote:
> On Thu, Nov 24, 2016 at 08:48:04AM -0700, Jeff Law wrote:
> > On 11/24/2016 07:53 AM, Segher Boessenkool wrote:
> > >
> > >That we compare different kinds of costs (which really has no meaning at
> > >all, it's a heuristic at best) in various places is a known problem, not
> > >a regression.
> > But the problems with the costing system exhibit themselves as a code
> > quality regression. In the end that's what the end-users see -- a
> > regression in the quality of the code GCC generates.
>
> Yes, exactly -- and I fear this all-encompassing change will cause just
> such a regression for many users. Tests are running, will know more
> later today (or tomorrow).
>
> The PR is about a very specific problem; the patch is not. The patch
> is not a bug fix. If we allow anything that "makes things better" in
> stage 3, what make it different from stage 1 then?
Here are results of testing with trunk right before the three patches,
compared with with the three patches. This lists the sizes of the vmlinux
of a Linux kernel build for that arch.
better:
blackfin 1973931 1973867
frv 3638192 3637792
h8300 1060172 1059976
i386 9742984 9742463
ia64 15402035 15396171
mips 4286748 4286692
mn10300 2360025 2358201
nios2 3185625 3176693
x86_64 10360418 10359588
worse:
alpha 5439003 5455979
c6x 2107939 2108931
cris 2189380 2193836
m32r 3427409 3427453
m68k 3228408 3230978
mips64 5564819 5565291
parisc 8278881 8289573
parisc64 7234619 7249139
powerpc 8438949 8440005
powerpc64 14499969 14508689
s390 12778748 12779220
shnommu 1369868 1371020
sparc64 5921556 5922172
tilegx 12297581 12307461
tilepro 11215603 11227339
xtensa 1776196 1779152
does not build:
arc 0 0
arm 0 0
arm64 0 0
microblaze 0 0
sh 0 0
sparc 0 0
Segher