[Bug target/65153] [SH][4.9 Regression] "insn does not satisfy its constraints" when compiling libmcrypt

[olegendo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65153

--- Comment #8 from Oleg Endo <olegendo at gcc dot gnu.org> ---
It seems that the problematic peephole is trying to wallpaper some unlucky
register allocation/reload choices like:

before peephole:
    mov.w    .L26,r1
    add    r8,r1
    mov    r1,r8
    mov    #0,r1
    mov.l    r1,@(32,r8)

after peephole:
    mov.w    .L26,r1
    add    r8,r1
    mov    #0,r8
    mov.l    r8,@(32,r1)

I've tried to disable the peephole on trunk and compared CSiBE results.  It
seems the peephole doesn't hit very often:
sum:  3371887 -> 3371943    +56 / +0.001661 %

So we could probably remove the complex peephole without a big loss.

I have a set of similar but simpler peepholes with a higher hit rate.  Maybe we
can replace the complex peephole with some simpler ones.