[Bug gas/30578] New: libavcodec/x86/mathops.h:125: Error: operand type mismatch for ` shr'

[mh-sourceware at glandium dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30578

            Bug ID: 30578
           Summary: libavcodec/x86/mathops.h:125: Error: operand type
                    mismatch for ` shr'
           Product: binutils
           Version: 2.41 (HEAD)
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gas
          Assignee: unassigned at sourceware dot org
          Reporter: mh-sourceware at glandium dot org
  Target Milestone: ---

Created attachment 14942
  --> https://sourceware.org/bugzilla/attachment.cgi?id=14942&action=edit
Generated assembly

This is a "regression" from:

commit c34d1cc9200ae24dc7572aaf77d80276c0490e9b
Author: Jan Beulich <jbeulich@suse.com>
Date:   Fri Feb 24 13:56:57 2023 +0100

    x86: restrict insn templates accepting negative 8-bit immediates

The code that fails to assemble comes from inline assembly from ffmpeg, and
compiled with GCC. I'm going to attach both the preprocessed C source, and the
generated assembly.

The failing instructions look like:
  shrl $-8, %eax

which, considering the commit, it not too surprising. The corresponding code in
C looks like:

static inline uint32_t NEG_USR32(uint32_t a, int8_t s){
    __asm__ ("shrl %1, %0\n\t"
         : "+r" (a)
         : "ic" ((uint8_t)(-s))
    );
    return a;
}


The question is open whether this is a problem in GCC, GAS, or ffmpeg. One
could argue in any direction, I guess. I'm starting with GAS, since it's a
change there that started this.

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