I am using MMX built-ins and gcc-4.0-20050825 and I am experiencing generation
of a lot of uneeded movq. I don't know which gcc snapshot introduced this, but a
I know that some pre-release gcc 4.0 didn't show this bad behaviour.
BTW, this is using gcc built-ins. The situation is much wors when using
intrinsics via mmintrin.h. (Again old pre4.0 gcc didn't have the problem;
using gcc builtins or mmintin.h intrinsics made no difference; both generated
nice code.)
LC_ALL=C i686-pc-linux-gnu-gcc-4.0.2-beta20050825 -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with:
/var/tmp/portage/gcc-4.0.2_beta20050825/work/gcc-4.0-20050825/configure
--prefix=/usr --bindir=/usr/i686-pc-linux-gnu/gcc-bin/4.0.2-beta20050825
--includedir=/usr/lib/gcc/i686-pc-linux-gnu/4.0.2-beta20050825/include
--datadir=/usr/share/gcc-data/i686-pc-linux-gnu/4.0.2-beta20050825
--mandir=/usr/share/gcc-data/i686-pc-linux-gnu/4.0.2-beta20050825/man
--infodir=/usr/share/gcc-data/i686-pc-linux-gnu/4.0.2-beta20050825/info
--with-gxx-include-dir=/usr/lib/gcc/i686-pc-linux-gnu/4.0.2-beta20050825/include/g++-v4
--host=i686-pc-linux-gnu --build=i686-pc-linux-gnu --disable-altivec
--enable-nls --without-included-gettext --with-system-zlib --disable-checking
--disable-werror --disable-libunwind-exceptions --disable-multilib
--disable-libgcj --enable-languages=c,c++ --enable-shared --enable-threads=posix
--enable-__cxa_atexit --enable-clocale=gnu
Thread model: posix
gcc version 4.0.2-beta20050825 (Gentoo 4.0.2_beta20050825)
i686-pc-linux-gnu-gcc-4.0.2-beta20050825 mixaudio16.c -save-temps -c -O2
-march=athlon-xp
Source:
typedef int v2si __attribute__ ((vector_size (8)));
typedef int di __attribute__ ((vector_size (8)));
typedef short v4hi __attribute__ ((vector_size (8)));
void MixAudio16_MMX_T(char* src1, char* src2, char* dst)
{
v4hi indata;
v4hi signmask;
v2si loout;
v2si hiout;
v2si temp;
__attribute__((aligned(16))) static const short sm[4] =
{0x8000,0x8000,0x8000,0x8000};
static const v4hi *m = (v4hi*)sm;
indata = *(v4hi*)src1;
signmask = (v4hi)__builtin_ia32_pand((di)indata, *(di*)m);
signmask = __builtin_ia32_pcmpeqw(signmask, *m);
loout = (v2si)__builtin_ia32_punpcklwd(indata, signmask);
hiout = (v2si)__builtin_ia32_punpckhwd(indata, signmask);
indata = *(v4hi*)src2;
signmask = (v4hi)__builtin_ia32_pand((di)indata, *(di*)m);
signmask = __builtin_ia32_pcmpeqw(signmask, *m);
temp = (v2si)__builtin_ia32_punpcklwd(indata, signmask);
loout = __builtin_ia32_paddd(loout, temp);
temp = (v2si)__builtin_ia32_punpckhwd(indata, signmask);
hiout = __builtin_ia32_paddd(hiout, temp);
*(v4hi*)dst = __builtin_ia32_packssdw(loout, hiout);
__builtin_ia32_emms();
return;
}
assembler:
00002e50 <MixAudio16_MMX_T>:
2e50: 55 push %ebp
2e51: 89 e5 mov %esp,%ebp
2e53: 83 ec 10 sub $0x10,%esp
2e56: 8b 15 04 00 00 00 mov 0x4,%edx
2e5c: 8b 45 08 mov 0x8(%ebp),%eax
2e5f: 0f 6f 10 movq (%eax),%mm2
2e62: 0f 6f ca movq %mm2,%mm1
2e65: 8b 45 0c mov 0xc(%ebp),%eax
2e68: 0f 7f 55 f8 movq %mm2,0xfffffff8(%ebp)
2e6c: 0f 6f 45 f8 movq 0xfffffff8(%ebp),%mm0
2e70: 0f db 02 pand (%edx),%mm0
2e73: 0f 7f 45 f0 movq %mm0,0xfffffff0(%ebp)
2e77: 0f 6f 45 f0 movq 0xfffffff0(%ebp),%mm0
2e7b: 0f 75 02 pcmpeqw (%edx),%mm0
2e7e: 0f 61 c8 punpcklwd %mm0,%mm1
2e81: 0f 69 d0 punpckhwd %mm0,%mm2
2e84: 0f 7f 4d f8 movq %mm1,0xfffffff8(%ebp)
2e88: 0f 6f 5d f8 movq 0xfffffff8(%ebp),%mm3
2e8c: 0f 7f 55 f8 movq %mm2,0xfffffff8(%ebp)
2e90: 0f 6f 10 movq (%eax),%mm2
2e93: 0f 6f 65 f8 movq 0xfffffff8(%ebp),%mm4
2e97: 0f 7f 55 f8 movq %mm2,0xfffffff8(%ebp)
2e9b: 0f 6f 45 f8 movq 0xfffffff8(%ebp),%mm0
2e9f: 0f 6f ca movq %mm2,%mm1
2ea2: 0f db 02 pand (%edx),%mm0
2ea5: 8b 45 10 mov 0x10(%ebp),%eax
2ea8: 0f 7f 45 f0 movq %mm0,0xfffffff0(%ebp)
2eac: 0f 6f 45 f0 movq 0xfffffff0(%ebp),%mm0
2eb0: 0f 75 02 pcmpeqw (%edx),%mm0
2eb3: 0f 61 c8 punpcklwd %mm0,%mm1
2eb6: 0f 69 d0 punpckhwd %mm0,%mm2
2eb9: 0f 7f 4d f8 movq %mm1,0xfffffff8(%ebp)
2ebd: 0f fe 5d f8 paddd 0xfffffff8(%ebp),%mm3
2ec1: 0f 7f 55 f8 movq %mm2,0xfffffff8(%ebp)
2ec5: 0f fe 65 f8 paddd 0xfffffff8(%ebp),%mm4
2ec9: 0f 6b dc packssdw %mm4,%mm3
2ecc: 0f 7f 18 movq %mm3,(%eax)
2ecf: 0f 77 emms
2ed1: c9 leave
2ed2: c3 ret
2ed3: 8d b6 00 00 00 00 lea 0x0(%esi),%esi
2ed9: 8d bc 27 00 00 00 00 lea 0x0(%edi),%edi
--
Summary: built-ins MMX regression
Product: gcc
Version: 4.0.2
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: prakash at punnoor dot de
CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i?86-*-*
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23630
