https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92825
Bug ID: 92825
Summary: Unnecesary stack protection and missed SLP
vectorization in Firefox's LightPixel.
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: hubicka at gcc dot gnu.org
Target Milestone: ---
Created attachment 47428
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47428&action=edit
full testcase
uint32_t DiffuseLightingSoftware::LightPixel(const Point3D& aNormal,
const Point3D& aVectorToLight,
uint32_t aColor) {
Float dotNL = std::max(0.0f, aNormal.DotProduct(aVectorToLight));
Float diffuseNL = mDiffuseConstant * dotNL;
union {
uint32_t bgra;
uint8_t components[4];
} color = {aColor};
color.components[B8G8R8A8_COMPONENT_BYTEOFFSET_B] = umin(
uint32_t(diffuseNL * color.components[B8G8R8A8_COMPONENT_BYTEOFFSET_B]),
255U);
color.components[B8G8R8A8_COMPONENT_BYTEOFFSET_G] = umin(
uint32_t(diffuseNL * color.components[B8G8R8A8_COMPONENT_BYTEOFFSET_G]),
255U);
color.components[B8G8R8A8_COMPONENT_BYTEOFFSET_R] = umin(
uint32_t(diffuseNL * color.components[B8G8R8A8_COMPONENT_BYTEOFFSET_R]),
255U);
color.components[B8G8R8A8_COMPONENT_BYTEOFFSET_A] = 255;
return color.bgra;
}
(full testcase attached)
Built with -O3 -fstack-protection-strong results in slower code with gcc10 than
with gcc9 or clang.
GCC produces:
│ 0000000004390e20 <mozilla::gfx::(anonymous
namespace)::SpecularLightingSoftware::LightPixel(mozilla::gfx::Point3DTyped<mozilla::gfx::UnknownUnits,
float> const&,
│
_ZN7mozilla3gfx12_GLOBAL__N_124SpecularLightingSoftware10LightPixelERKNS0_12Point3DTypedINS0_12UnknownUnitsEfEES7_j():
0.19 │ push %rbp
0.60 │ pxor %xmm5,%xmm5
0.05 │ mov %rsp,%rbp
0.12 │ push %rbx
0.65 │ sub $0x18,%rsp
0.33 │ movss 0x4(%rdx),%xmm0
0.10 │ movss (%rdx),%xmm1
0.58 │ mov %fs:0x28,%rax
0.03 │ mov %rax,-0x18(%rbp)
0.22 │ xor %eax,%eax
0.07 │ movss pw_32+0x1588,%xmm3
1.58 │ addss 0x8(%rdx),%xmm3
0.67 │ addss %xmm5,%xmm0
0.23 │ addss %xmm5,%xmm1
│ movaps %xmm0,%xmm2
0.41 │ movaps %xmm1,%xmm4
0.87 │ mulss %xmm0,%xmm2
0.28 │ mulss %xmm1,%xmm4
3.71 │ addss %xmm2,%xmm4
0.14 │ movaps %xmm3,%xmm2
0.04 │ mulss %xmm3,%xmm2
1.99 │ addss %xmm2,%xmm4
0.15 │ movss 0x4(%rsi),%xmm2
9.39 │ sqrtss %xmm4,%xmm4
8.90 │ divss %xmm4,%xmm0
2.10 │ divss %xmm4,%xmm3
1.08 │ mulss %xmm0,%xmm2
0.01 │ movss 0x8(%rsi),%xmm0
while clang
Percent│
_ZN7mozilla3gfx12_GLOBAL__N_124SpecularLightingSoftware10LightPixelERKNS0_12Point3DTypedINS0_12UnknownUnitsEfEES7_j():
0.11 │ xorps %xmm0,%xmm0
0.83 │ movss 0x4(%rdx),%xmm1
3.29 │ addss %xmm0,%xmm1
0.03 │ movss (%rdx),%xmm2
0.08 │ movss 0x8(%rdx),%xmm3
0.04 │ unpcklps %xmm2,%xmm3
0.59 │ movss
mozilla::gfx::ConvertComponentTransferFunctionToFilter(mozilla::gfx::ComponentTransferAttributes
const&, int, int, mozilla::gfx::DrawTarget*, RefPtr<m
1.00 │ addps %xmm2,%xmm3
0.10 │ movaps %xmm3,%xmm4
0.82 │ shufps $0xe5,%xmm3,%xmm4
3.05 │ mulss %xmm4,%xmm4
0.09 │ movaps %xmm1,%xmm5
0.12 │ mulss %xmm1,%xmm5
2.77 │ addss %xmm4,%xmm5
0.06 │ movaps %xmm3,%xmm4
0.00 │ mulss %xmm3,%xmm4
2.95 │ addss %xmm5,%xmm4
9.54 │ sqrtss %xmm4,%xmm4
8.84 │ divss %xmm4,%xmm1
0.08 │ shufps $0xe0,%xmm4,%xmm4
2.45 │ divps %xmm4,%xmm3
0.88 │ mulss 0x4(%rsi),%xmm1
0.01 │ movss (%rsi),%xmm4
│ movss 0x8(%rsi),%xmm5
0.02 │ unpcklps %xmm4,%xmm5
2.82 │ mulps %xmm3,%xmm5
0.03 │ movaps %xmm5,%xmm3
0.88 │ shufps $0xe5,%xmm5,%xmm3
3.47 │ addss %xmm1,%xmm3
3.39 │ addss %xmm5,%xmm3
3.09 │ cmpless %xmm3,%xmm0
1.77 │ andps %xmm2,%xmm0
3.01 │ mulss %xmm3,%xmm0
3.25 │ mulss
mozIGeckoMediaPluginService::COMTypeInfo<mozIGeckoMediaPluginService,
void,%xmm0
4.85 │ cvttss2si %xmm0,%eax
