On Sun, 2020-08-23 at 00:24 +0100, Roger Sayle wrote:
> Hi Dave,
> I actually think using plus_xor_ior operator is useful. It means that if
> combine,
> inlining or some other RTL simplification generates these variants, these
> forms
> will still be recognized by the backend. It's more typing, but the compiler
> produces
> better code.
>
> Here's what I have so far, but please feel free to modify anything. I'll
> leave the
> rest to you.
>
> With this patch:
>
> unsigned long long rotl4(unsigned long long x)
> {
> return (x<<4) | (x>>60);
> }
>
> unsigned long long rotr4(unsigned long long x)
> {
> return (x<<60) | (x>>4);
> }
>
> which previously generated:
>
> rotl4: depd,z %r26,59,60,%r28
> extrd,u %r26,3,4,%r26
> bve (%r2)
> or %r26,%r28,%r28
>
> rotr4: extrd,u %r26,59,60,%r28
> depd,z %r26,3,4,%r26
> bve (%r2)
> or %r26,%r28,%r28
>
> now produces:
>
> rotl4: bve (%r2)
> shrpd %r26,%r26,60,%r28
>
> rotr4: bve (%r2)
> shrpd %r26,%r26,4,%r28
>
>
> I'm guessing this is very similar to what you were thinking (or what I
> described previously).
>
> Many thanks again for trying out these patches/suggestions for me.
So I put this one into the tester overnight.
It 3-stages, but trips:
Tests that now fail, but worked before (5 tests):
gcc.dg/tree-ssa/slsr-13.c scan-tree-dump-times optimized " \\* 4" 2
gcc.dg/tree-ssa/slsr-13.c scan-tree-dump-times optimized " \\* 4" 2
gcc.dg/tree-ssa/slsr-13.c scan-tree-dump-times optimized " \\* 5" 0
gcc.dg/tree-ssa/slsr-13.c scan-tree-dump-times optimized " \\* 5" 0
gcc.target/hppa/shadd-2.c scan-assembler-times sh.add 2
I think we've already discussed shadd-2. It's not immediately clear if the slsr
failure is due to this change or something different -- the latter seems like a
definite possibility as we're changing things as we leave gimple, but the test
is
checking the result of the gimple optimizers.
Your call on how to proceed. I can put additional patches into the tester
easily, so if you've got something you want investigated, don't hesitate to
reach
out.
jeff
