From 02ae8b78ff311144bc915a96889db66f46eca208 Mon Sep 17 00:00:00 2001 From: Reid Spencer Date: Thu, 17 May 2007 06:26:29 +0000 Subject: [PATCH] For lshr by 0 bits, just return *this as a short cut. This also prevents undefined behavior when the width > 64 bits. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37153 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Support/APInt.cpp | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/lib/Support/APInt.cpp b/lib/Support/APInt.cpp index 460cf557610..2ed9b07f1ea 100644 --- a/lib/Support/APInt.cpp +++ b/lib/Support/APInt.cpp @@ -1149,6 +1149,12 @@ APInt APInt::lshr(uint32_t shiftAmt) const { if (shiftAmt == BitWidth) return APInt(BitWidth, 0); + // If none of the bits are shifted out, the result is *this. This avoids + // issues with shifting byt he size of the integer type, which produces + // undefined results in the code below. This is also an optimization. + if (shiftAmt == 0) + return *this; + // Create some space for the result. uint64_t * val = new uint64_t[getNumWords()];