From 8398512f89623144c8bb45ce9deb4f74f76480fc Mon Sep 17 00:00:00 2001 From: Benjamin Kramer Date: Wed, 30 Mar 2011 17:02:54 +0000 Subject: Avoid turning a floating point division with a constant power of two into a denormal multiplication. Some platforms may treat denormals as zero, on other platforms multiplication with a subnormal is slower than dividing by a normal. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128555 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Support/APFloat.cpp | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'lib/Support/APFloat.cpp') diff --git a/lib/Support/APFloat.cpp b/lib/Support/APFloat.cpp index abe5575318..3a63258cd2 100644 --- a/lib/Support/APFloat.cpp +++ b/lib/Support/APFloat.cpp @@ -3583,6 +3583,14 @@ bool APFloat::getExactInverse(APFloat *inv) const { if (reciprocal.divide(*this, rmNearestTiesToEven) != opOK) return false; + // Avoid multiplication with a denormal, it is not safe on all platforms and + // may be slower than a normal division. + if (reciprocal.significandMSB() + 1 < reciprocal.semantics->precision) + return false; + + assert(reciprocal.category == fcNormal && + reciprocal.significandLSB() == reciprocal.semantics->precision - 1); + if (inv) *inv = reciprocal; -- cgit v1.2.3-70-g09d2