Hi,
the following input compiles OK with -O:
------------8<----------8<-------------8<-------------
# 1 "jidctint.c"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "jidctint.c"
volatile static unsigned long long fix_029_n089n196 = 0x098ea46e098ea46e;
__inline void domidct8x8llmW();
void
jpeg_idct_islow ()
{
domidct8x8llmW();
}
__inline void domidct8x8llmW()
{
__asm__ (
"pmaddwd fix_029_n089n196,%%mm7 \n\t"
"emms \n\t"
:
);
}
------------8<----------8<-------------8<-------------
(/usr/local/bin/gcc -O1 -v -save-temps -I. -c -o jidctint.o jidctint.c
Reading specs from /usr/local/lib/gcc/i686-pc-linux-gnu/3.4.3/specs
Configured with: /home/ltg/software/src/work/gcc-3.4.3/configure
--enable-threads=posix --enable-libgcj --enable-shared --enable-__cxa_atexit
--enable-version-specific-runtime-libs --enable-checking
--enable-gather-detailed-mem-stats--disable-nls
--enable-languages=c,c++,f77,objc,java --enable-libgcj-multifile --with-x
--enable-java-awt=gtk,xlib
Thread model: posix
gcc version 3.4.3
/usr/local/libexec/gcc/i686-pc-linux-gnu/3.4.3/cc1 -E -quiet -v -I. jidctint.c
-mtune=pentiumpro -O1 -o jidctint.i
ignoring nonexistent directory "NONE/include"
ignoring nonexistent directory
"/usr/local/lib/gcc/i686-pc-linux-gnu/3.4.3/../../../../i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
.
/usr/local/include
/usr/local/lib/gcc/i686-pc-linux-gnu/3.4.3/include
/usr/include
End of search list.
/usr/local/libexec/gcc/i686-pc-linux-gnu/3.4.3/cc1 -fpreprocessed jidctint.i
-quiet -dumpbase jidctint.c -mtune=pentiumpro -auxbase-strip jidctint.o -O1
-version -o jidctint.s
GNU C version 3.4.3 (i686-pc-linux-gnu)
compiled by GNU C version 3.4.3.
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
jidctint.c:2: warning: integer constant is too large for "long" type
/usr/local/lib/gcc/i686-pc-linux-gnu/3.4.3/../../../../i686-pc-linux-gnu/bin/as
-V -Qy -o jidctint.o jidctint.s
GNU assembler version 2.15 (i686-pc-linux-gnu) using BFD version 2.15)
For the above piece of code I get the following assembler code:
------------8<----------8<-------------8<-------------
.file "jidctint.c"
.data
.align 8
.type fix_029_n089n196, @object
.size fix_029_n089n196, 8
fix_029_n089n196:
.quad 0x98ea46e098ea46e
.text
.globl jpeg_idct_islow
.type jpeg_idct_islow, @function
jpeg_idct_islow:
pushl %ebp
movl %esp, %ebp
subl $8, %esp
call domidct8x8llmW
leave
ret
.size jpeg_idct_islow, .-jpeg_idct_islow
.globl domidct8x8llmW
.type domidct8x8llmW, @function
domidct8x8llmW:
pushl %ebp
movl %esp, %ebp
#APP
pmaddwd fix_029_n089n196,%mm7
emms
#NO_APP
popl %ebp
ret
.size domidct8x8llmW, .-domidct8x8llmW
.section .note.GNU-stack,"",@progbits
.ident "GCC: (GNU) 3.4.3"
------------8<----------8<-------------8<-------------
When I compile the same piece of code with -O2 and above, I get:
------------8<----------8<-------------8<-------------
.file "jidctint.c"
.text
.p2align 4,,15
.globl domidct8x8llmW
.type domidct8x8llmW, @function
domidct8x8llmW:
pushl %ebp
movl %esp, %ebp
#APP
pmaddwd fix_029_n089n196,%mm7
emms
#NO_APP
popl %ebp
ret
.size domidct8x8llmW, .-domidct8x8llmW
.p2align 4,,15
.globl jpeg_idct_islow
.type jpeg_idct_islow, @function
jpeg_idct_islow:
pushl %ebp
movl %esp, %ebp
#APP
pmaddwd fix_029_n089n196,%mm7
emms
#NO_APP
popl %ebp
ret
.size jpeg_idct_islow, .-jpeg_idct_islow
.section .note.GNU-stack,"",@progbits
.ident "GCC: (GNU) 3.4.3"
------------8<----------8<-------------8<-------------
That means the optimizer eats
fix_029_n089n196:
.quad 0x98ea46e098ea46e
.text
which causes an "undefined reference to 'fix_029_n089n196'" later
when linking the executable.
Can you check this?
Thanks.
Lothar
--
Summary: gcc 3.4.3 optimizes volatile vars away (gcc 3.4.3 >= -
O2)
Product: gcc
Version: 3.4.3
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: ltg at zes dot uni-bremen dot de
CC: gcc-bugs at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20523
