On Wed, Apr 16, 2025 at 08:52:17PM +0200, Jakub Jelinek wrote:
> The following testcase ICEs since r15-1579 (addition of late combiner),
> because *clrmem_short can't be split.
> The problem is that the define_insn uses
> (use (match_operand 1 "nonmemory_operand" "n,a,a,a"))
> (use (match_operand 2 "immediate_operand" "X,R,X,X"))
> (clobber (match_scratch:P 3 "=X,X,X,&a"))
> and define_split assumed that if operands[1] is const_int_operand,
> match_scratch will be always scratch, and it will be reg only if
> it was the last alternative where operands[1] is a reg.
> The pattern doesn't guarantee it though, of course RA will not try to
> uselessly assign a reg there if it is not needed, but during RA
> on the testcase below we match the last alternative, but then comes
> late combiner and propagates const_int 3 into operands[1]. And that
> matches fine, match_scratch matches either scratch or reg and the constraint
> in that case is X for the first variant, so still just fine. But we won't
> split that because the splitters only expect scratch.
>
> The following patch fixes it by using match_scratch instead of scratch,
> so that it accepts either.
>
> Bootstrapped on s390x-linux, ok for trunk if regtesting passes as well?
Regtested successfully as well.
> 2025-04-16 Jakub Jelinek <ja...@redhat.com>
>
> PR target/119834
> * config/s390/s390.md (define_split after *cpymem_short): Use
> (clobber (match_scratch N)) instead of (clobber (scratch)). Use
> (match_dup 4) and operands[4] instead of (match_dup 3) and operands[3]
> in the last of those.
> (define_split after *clrmem_short): Use (clobber (match_scratch N))
> instead of (clobber (scratch)).
> (define_split after *cmpmem_short): Likewise.
>
> * g++.target/s390/pr119834.C: New test.
Jakub
