[Bug middle-end/82089] emit_cstore sign-extends BImode result for STORE_FLAG_VALUE == 1

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82089

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
Created attachment 42108
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42108&action=edit
minimal patch

This patch addresses the issue in a point-fix manner. With this patch, we
generate instead:
...
(insn 7 6 8 (set (reg:BI 62)
        (ne:BI (reg/v:SI 58 [ aD.1438 ])
            (reg/v:SI 59 [ bD.1439 ]))) "test.c":4 -1
     (nil))

(insn 8 7 9 (set (reg:SI 61)
        (zero_extend:SI (reg:BI 62))) "test.c":4 -1
     (nil))

(insn 9 8 10 (set (reg:SI 57 [ <retval> ])
        (reg:SI 61)) "test.c":4 -1
     (nil))
...