[llvm] r240420 - SystemZ: Avoid left shifting negative values (it's UB)

[Justin Bogner]

Author: bogner
Date: Tue Jun 23 10:38:24 2015
New Revision: 240420

URL: http://llvm.org/viewvc/llvm-project?rev=240420&view=rev
Log:
SystemZ: Avoid left shifting negative values (it's UB)

Found by ubsan.

Modified:
    llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp

Modified: llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp?rev=240420&r1=240419&r2=240420&view=diff
==============================================================================
--- llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp Tue Jun 23 10:38:24 2015
@@ -2005,17 +2005,17 @@ static Comparison getIntrinsicCmp(Select
   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;