https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78311
Bug ID: 78311
Summary: "register value used as expression" on i386 in inline
assembly statement with "o" constraint
Product: gcc
Version: 6.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: inline-asm
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc at abeckmann dot de
Target Milestone: ---
This is a regression from GCC 5 on i386.
This code example has been minimized from uqm source which fails to build with
gcc-6 (but succeeds with gcc-5):
========== 8< ==========
extern unsigned int A [ 42 ] ;
void f ()
{
__asm__ ( "movd %0 (, %%edx, 4), %%mm0 \n\t" : : "o" (*A) : "%edx" ) ;
}
========== >8 ==========
$ gcc-5 -m32 -W -Wall -c constraint-o.c ; echo $?
0
$ gcc-6 -m32 -W -Wall -c constraint-o.c; echo $?
constraint-o.c: Assembler messages:
constraint-o.c:4: Error: register value used as expression
1
========== assembly generated by gcc-5 -S ==========
.globl f
.type f, @function
f:
.LFB0:
.cfi_startproc
pushl %ebp
.cfi_def_cfa_offset 8
.cfi_offset 5, -8
movl %esp, %ebp
.cfi_def_cfa_register 5
#APP
# 4 "constraint-o.c" 1
movd A (, %edx, 4), %mm0
# 0 "" 2
#NO_APP
nop
popl %ebp
.cfi_restore 5
.cfi_def_cfa 4, 4
ret
.cfi_endproc
==========
========== assembly generated by gcc-6 -S ==========
.globl f
.type f, @function
f:
.LFB0:
.cfi_startproc
pushl %ebp
.cfi_def_cfa_offset 8
.cfi_offset 5, -8
movl %esp, %ebp
.cfi_def_cfa_register 5
call __x86.get_pc_thunk.ax
addl $_GLOBAL_OFFSET_TABLE_, %eax
movl A@GOT(%eax), %eax
#APP
# 4 "constraint-o.c" 1
movd (%eax) (, %edx, 4), %mm0
# 0 "" 2
#NO_APP
nop
popl %ebp
.cfi_restore 5
.cfi_def_cfa 4, 4
ret
.cfi_endproc
==========
$ gcc-6 --version
gcc-6 (Debian 6.2.0-10) 6.2.0 20161027
$ gcc-5 --version
gcc-5 (Debian 5.4.1-3) 5.4.1 20161019
