Re: [PATCH] builtins: Fix up ICE in inline_string_cmp [PR109258]

[Richard Biener <rguenther@suse.de>]

On Fri, 24 Mar 2023, Jakub Jelinek wrote:

> Hi!
> 
> The PR109086 r13-6690 inline_string_cmp change to
>       if (diff != result)
> 	emit_move_insn (result, diff);
> regressed
> FAIL: go.test/test/fixedbugs/bug207.go,  -O2 -g  (internal compiler error: in emit_move_insn, at expr.cc:4224)
> The problem is the Go FE doesn't mark __builtin_memcmp as pure (I'll also
> send patch for that) and so result is const0_rtx when the call lost its lhs
> and the above move ICEs because moving something into const0_rtx is obviously
> invalid.
> I think it is better not to rely on all FEs having these *cmp functions
> pure anD DCE being performed.  The following patch just punts from the
> inline expansion in that case, so we just emit normal library call.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

> 2023-03-24  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR middle-end/109258
> 	* builtins.cc (inline_expand_builtin_bytecmp): Return NULL_RTX early
> 	if target == const0_rtx.
> 
> --- gcc/builtins.cc.jj	2023-03-23 10:00:58.308100548 +0100
> +++ gcc/builtins.cc	2023-03-23 11:05:38.308135309 +0100
> @@ -7178,8 +7178,8 @@ inline_expand_builtin_bytecmp (tree exp,
>    bool is_ncmp = (fcode == BUILT_IN_STRNCMP || fcode == BUILT_IN_MEMCMP);
>  
>    /* Do NOT apply this inlining expansion when optimizing for size or
> -     optimization level below 2.  */
> -  if (optimize < 2 || optimize_insn_for_size_p ())
> +     optimization level below 2 or if unused *cmp hasn't been DCEd.  */
> +  if (optimize < 2 || optimize_insn_for_size_p () || target == const0_rtx)
>      return NULL_RTX;
>  
>    gcc_checking_assert (fcode == BUILT_IN_STRCMP
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
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