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bug #1191 - Prevent Clang/ARM from rewriting VMLA into VMUL+VADD

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This commit is contained in:
Benoit Jacob 2016-04-04 16:41:47 -04:00
parent c4179dd470
commit 03f2997a11
1 changed files with 19 additions and 1 deletions
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20
Eigen/src/Core/arch/NEON/PacketMath.h
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@ -186,7 +186,25 @@ template<> EIGEN_STRONG_INLINE Packet4i pdiv<Packet4i>(const Packet4i& /*a*/, co
// MLA: 10 GFlop/s ; FMA: 12 GFlops/s. // MLA: 10 GFlop/s ; FMA: 12 GFlops/s.
template<> EIGEN_STRONG_INLINE Packet4f pmadd(const Packet4f& a, const Packet4f& b, const Packet4f& c) { return vfmaq_f32(c,a,b); } template<> EIGEN_STRONG_INLINE Packet4f pmadd(const Packet4f& a, const Packet4f& b, const Packet4f& c) { return vfmaq_f32(c,a,b); }
#else #else
template<> EIGEN_STRONG_INLINE Packet4f pmadd(const Packet4f& a, const Packet4f& b, const Packet4f& c) { return vmlaq_f32(c,a,b); } template<> EIGEN_STRONG_INLINE Packet4f pmadd(const Packet4f& a, const Packet4f& b, const Packet4f& c) {
#if EIGEN_COMP_CLANG && EIGEN_ARCH_ARM
// Clang/ARM will replace VMLA by VMUL+VADD at least for some values of -mcpu,
// at least -mcpu=cortex-a8 and -mcpu=cortex-a7. Since the former is the default on
// -march=armv7-a, that is a very common case.
// See e.g. this thread:
// http://lists.llvm.org/pipermail/llvm-dev/2013-December/068806.html
Packet4f r = c;
asm volatile(
"vmla.f32 %q[r], %q[a], %q[b]"
: [r] "+w" (r)
: [a] "w" (a),
[b] "w" (b)
: );
return r;
#else
return vmlaq_f32(c,a,b);
#endif
}
#endif #endif
// No FMA instruction for int, so use MLA unconditionally. // No FMA instruction for int, so use MLA unconditionally.