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 <jbeul...@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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