Under some conditions (generally if you upset the inlining heuristic ie by force
inlining something), SSE intrinsics don't get inlined and some truely horrible
code ensues; the fix, tinkering with params, isn't much prettier.
Happened to me with various 4.x versions, on x86 or x86-64.
silly testcase:
#include <xmmintrin.h>
static __attribute__ ((always_inline)) bool bloatit(const __m128 a, const __m128
b) {
const __m128
v0 = _mm_max_ps(a,b),
v1 = _mm_min_ps(a,b),
v2 = _mm_mul_ps(a,b),
v3 = _mm_div_ps(a,b),
g0 = _mm_or_ps(_mm_or_ps(_mm_or_ps(v0,v1), v2), v3);
return _mm_movemask_ps(g0);
}
bool finalblow(const __m128 a, const __m128 b, const __m128 c, const __m128 d,
const __m128 e, const __m128 f) {
return bloatit(a,b) & bloatit(c,d) & bloatit(e,f) & bloatit(a,c) &
bloatit(b,d)
& bloatit(c,e) & bloatit(d,f);
}
int main() { return 0; }
At -O3, on x86-64-linux, g++-4120050417 gets funky with:
0000000000400540 <_mm_mul_ps(float __vector, float __vector)>:
400540: mulps %xmm1,%xmm0
400543: retq
...
0000000000400550 <_mm_div_ps(float __vector, float __vector)>:
400550: divps %xmm1,%xmm0
400553: retq
...
0000000000400560 <_mm_min_ps(float __vector, float __vector)>:
400560: minps %xmm1,%xmm0
400563: retq
...
0000000000400570 <_mm_max_ps(float __vector, float __vector)>:
400570: maxps %xmm1,%xmm0
400573: retq
...
0000000000400580 <_mm_or_ps(float __vector, float __vector)>:
400580: orps %xmm1,%xmm0
400583: retq
...
0000000000400590 <_mm_movemask_ps(float __vector)>:
400590: movmskps %xmm0,%eax
400593: retq
... only to conclude with this wonder
00000000004005b0 <finalblow(float __vector, float __vector, float __vector,
float __vector, float __vector, float __vector)>:
4005b0: push %rbx
4005b1: xor %ebx,%ebx
4005b3: sub $0x1b0,%rsp
4005ba: movaps %xmm2,0x180(%rsp)
4005c2: movaps %xmm3,0x170(%rsp)
4005ca: movaps %xmm4,0x160(%rsp)
4005d2: movaps %xmm5,0x150(%rsp)
4005da: movaps %xmm1,0x190(%rsp)
4005e2: movaps %xmm0,0x1a0(%rsp)
4005ea: callq 400550 <_mm_div_ps(float __vector, float __vector)>
4005ef: movaps %xmm0,0x140(%rsp)
4005f7: movaps 0x190(%rsp),%xmm1
4005ff: movaps 0x1a0(%rsp),%xmm0
400607: callq 400540 <_mm_mul_ps(float __vector, float __vector)>
40060c: movaps 0x190(%rsp),%xmm1
400614: movaps %xmm0,0x130(%rsp)
40061c: movaps 0x1a0(%rsp),%xmm0
400624: callq 400560 <_mm_min_ps(float __vector, float __vector)>
400629: movaps 0x190(%rsp),%xmm1
400631: movaps %xmm0,0x120(%rsp)
400639: movaps 0x1a0(%rsp),%xmm0
400641: callq 400570 <_mm_max_ps(float __vector, float __vector)>
400646: movaps 0x120(%rsp),%xmm1
40064e: callq 400580 <_mm_or_ps(float __vector, float __vector)>
400653: movaps 0x130(%rsp),%xmm1
40065b: callq 400580 <_mm_or_ps(float __vector, float __vector)>
400660: movaps 0x140(%rsp),%xmm1
400668: callq 400580 <_mm_or_ps(float __vector, float __vector)>
40066d: callq 400590 <_mm_movemask_ps(float __vector)>
400672: movaps 0x170(%rsp),%xmm1
etc...
As said earlier, that's just one way to make that happen.
It would be a real plus if those intrinsics could be inconditionnaly inlined.
--
Summary: SSE intrinsics not inlined, sometimes.
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: other
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: tbptbp at gmail dot com
CC: gcc-bugs at gcc dot gnu dot org
GCC host triplet: x86*
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21195
