From cac03419a614ad60205d8d55daa3f9e7cc3cc7f1 Mon Sep 17 00:00:00 2001 From: Justin Bogner Date: Wed, 24 Jun 2015 05:59:19 +0000 Subject: [PATCH] SystemZ: Rephrase this allOnes calculation to avoid UB This allOnes function hits undefined behaviour if Count is greater than 64, but we can avoid that and simplify the calculation by just saturating if such a value is passed in. This comes up under ubsan becauseRxSBGOperands is sometimes created with values that are 128 bits wide. Somebody more familiar with this code should probably look into whether that's expected, as a 64 bit mask may or may not be appropriate for such types. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240520 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Target/SystemZ/SystemZISelDAGToDAG.cpp | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp b/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp index 0eb3d6593fe..26c9c9b9f67 100644 --- a/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp +++ b/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp @@ -96,7 +96,9 @@ struct SystemZAddressingMode { // Return a mask with Count low bits set. static uint64_t allOnes(unsigned int Count) { - return Count == 0 ? 0 : (uint64_t(1) << (Count - 1) << 1) - 1; + if (Count > 63) + return UINT64_MAX; + return (uint64_t(1) << Count) - 1; } // Represents operands 2 to 5 of the ROTATE AND ... SELECTED BITS operation