From: Justin Bogner <mail@justinbogner.com>
Date: Tue, 23 Jun 2015 15:38:24 +0000 (+0000)
Subject: SystemZ: Avoid left shifting negative values (it's UB)
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=3800e768a2fe4f924f80aaad985d9160e3267f02;p=oota-llvm.git

SystemZ: Avoid left shifting negative values (it's UB)

Found by ubsan.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240420 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/SystemZ/SystemZISelLowering.cpp b/lib/Target/SystemZ/SystemZISelLowering.cpp
index 91e12c2d9d7..372f6fb3ea5 100644
--- a/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -2005,17 +2005,17 @@ static Comparison getIntrinsicCmp(SelectionDAG &DAG, unsigned Opcode,
   else if (Cond == ISD::SETLT || Cond == ISD::SETULT)
     // bits above bit 3 for CC==0 (always false), bits above bit 0 for CC==3,
     // always true for CC>3.
-    C.CCMask = CC < 4 ? -1 << (4 - CC) : -1;
+    C.CCMask = CC < 4 ? ~0U << (4 - CC) : -1;
   else if (Cond == ISD::SETGE || Cond == ISD::SETUGE)
     // ...and the inverse of that.
-    C.CCMask = CC < 4 ? ~(-1 << (4 - CC)) : 0;
+    C.CCMask = CC < 4 ? ~(~0U << (4 - CC)) : 0;
   else if (Cond == ISD::SETLE || Cond == ISD::SETULE)
     // bit 3 and above for CC==0, bit 0 and above for CC==3 (always true),
     // always true for CC>3.
-    C.CCMask = CC < 4 ? -1 << (3 - CC) : -1;
+    C.CCMask = CC < 4 ? ~0U << (3 - CC) : -1;
   else if (Cond == ISD::SETGT || Cond == ISD::SETUGT)
     // ...and the inverse of that.
-    C.CCMask = CC < 4 ? ~(-1 << (3 - CC)) : 0;
+    C.CCMask = CC < 4 ? ~(~0U << (3 - CC)) : 0;
   else
     llvm_unreachable("Unexpected integer comparison type");
   C.CCMask &= CCValid;