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bug #1190 - Don't trust __ARM_FEATURE_FMA on Clang/ARM

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This commit is contained in:
Benoit Jacob 2016-04-04 16:42:40 -04:00
parent 03f2997a11
commit 158fea0f5e
1 changed files with 3 additions and 1 deletions
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4
Eigen/src/Core/arch/NEON/PacketMath.h
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@ -177,7 +177,9 @@ template<> EIGEN_STRONG_INLINE Packet4i pdiv<Packet4i>(const Packet4i& /*a*/, co
return pset1<Packet4i>(0);
}
#ifdef __ARM_FEATURE_FMA
// Clang/ARM wrongly advertises __ARM_FEATURE_FMA even when it's not available,
// then implements a slow software scalar fallback calling fmaf()!
#if (defined __ARM_FEATURE_FMA) && !(EIGEN_COMP_CLANG && EIGEN_ARCH_ARM)
// See bug 936.
// FMA is available on VFPv4 i.e. when compiling with -mfpu=neon-vfpv4.
// FMA is a true fused multiply-add i.e. only 1 rounding at the end, no intermediate rounding.