From: Chandler Carruth <chandlerc@gmail.com>
Date: Mon, 9 Jan 2012 09:47:25 +0000 (+0000)
Subject: Don't rely on the fact that shift values are never very large, and thus
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4e3a40293f2e6f04396d2c7d355c5f2a03488c87;p=oota-llvm.git

Don't rely on the fact that shift values are never very large, and thus
this substraction will result in small negative numbers at worst which
become very large positive numbers on assignment and are thus caught by
the <=4 check on the next line. The >0 check clearly intended to catch
these as negative numbers.

Spotted by inspection, and impossible to trigger given the shift widths
that can be used.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147773 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index 3c35763f82d..1cc19b25d5e 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -996,7 +996,7 @@ bool X86DAGToDAGISel::MatchAddressRecursively(SDValue N, X86ISelAddressMode &AM,
     // allows us to convert the shift and and into an h-register extract and
     // a scaled index.
     if (Shift.getOpcode() == ISD::SRL && Shift.hasOneUse()) {
-      unsigned ScaleLog = 8 - C1->getZExtValue();
+      int ScaleLog = 8 - C1->getZExtValue();
       if (ScaleLog > 0 && ScaleLog < 4 &&
           C2->getZExtValue() == (UINT64_C(0xff) << ScaleLog)) {
         SDValue Eight = CurDAG->getConstant(8, MVT::i8);