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From: "elronnd at elronnd dot net" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/97607] New: Spurious sign extension
Date: Tue, 27 Oct 2020 23:54:55 +0000
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X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 11.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97607

            Bug ID: 97607
           Summary: Spurious sign extension
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: elronnd at elronnd dot net
  Target Milestone: ---

The following code

extern void fun(char);=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
void wrapper(char x) { fun(x); }

Should compile 'wrapper' to a single jump, but instead it does this (on amd=
64):

wrapper:
        movsx   edi, dil
        jmp     fun

Presumably 'x' is getting promoted to int in wrapper, and the promotion nev=
er
gets removed.=