[Bug rtl-optimization/78437] [7 Regression]: Invalid sign-extend conversion in REE pass

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78437

--- Comment #4 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Eric Botcazou from comment #3)
> Created attachment 40098 [details]
> Tentative fix
> 
> It only affects Alpha (by default) but I no longer have access to Alpha
> hardware so I'm going to play with it on SPARC.  Its effect on the assembly
> code on Alpha is:
> 
> --- pr78437_1.s 2016-11-21 11:54:33.678363106 +0100
> +++ pr78437_2.s 2016-11-21 11:54:40.230542615 +0100
> @@ -62,7 +62,7 @@
>         ldbu $7,max($5)         !gprellow
>         sextb $8,$3
>         stb $8,expected($2)             !gprellow
> -       mov $3,$22
> +       bis $31,$8,$22
>         sextb $7,$7
>         cmpeq $3,$7,$3
>         beq $3,$L4
> 
> FWIW the change for PR rtl-opt/59461 eliminated 2 redundant extensions.

Yes this change fixes reduced testcase execution.

I have started bootstrap+regtest with your patch on alpha native. Please expect
results sometime tomorrow.