[llvm] r216131 - Fix undefined behavior (left shift of negative value) in SystemZ backend.

[Alexey Samsonov]

Author: samsonov
Date: Wed Aug 20 16:56:43 2014
New Revision: 216131

URL: http://llvm.org/viewvc/llvm-project?rev=216131&view=rev
Log:
Fix undefined behavior (left shift of negative value) in SystemZ backend.

This bug is reported by UBSan.

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

Modified: llvm/trunk/lib/Target/SystemZ/SystemZFrameLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/SystemZ/SystemZFrameLowering.cpp?rev=216131&r1=216130&r2=216131&view=diff
==============================================================================
--- llvm/trunk/lib/Target/SystemZ/SystemZFrameLowering.cpp (original)
+++ llvm/trunk/lib/Target/SystemZ/SystemZFrameLowering.cpp Wed Aug 20 16:56:43 2014
@@ -294,7 +294,7 @@ static void emitIncrement(MachineBasicBl
     else {
       Opcode = SystemZ::AGFI;
       // Make sure we maintain 8-byte stack alignment.
-      int64_t MinVal = -int64_t(1) << 31;
+      int64_t MinVal = -uint64_t(1) << 31;
       int64_t MaxVal = (int64_t(1) << 31) - 8;
       if (ThisVal < MinVal)
         ThisVal = MinVal;

Modified: llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp?rev=216131&r1=216130&r2=216131&view=diff
==============================================================================
--- llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/SystemZ/SystemZISelLowering.cpp Wed Aug 20 16:56:43 2014
@@ -2800,14 +2800,10 @@ SystemZTargetLowering::emitAtomicLoadBin
     unsigned Tmp = MRI.createVirtualRegister(RC);
     BuildMI(MBB, DL, TII->get(BinOpcode), Tmp)
       .addReg(RotatedOldVal).addOperand(Src2);
-    if (BitSize < 32)
+    if (BitSize <= 32)
       // XILF with the upper BitSize bits set.
       BuildMI(MBB, DL, TII->get(SystemZ::XILF), RotatedNewVal)
-        .addReg(Tmp).addImm(uint32_t(~0 << (32 - BitSize)));
-    else if (BitSize == 32)
-      // XILF with every bit set.
-      BuildMI(MBB, DL, TII->get(SystemZ::XILF), RotatedNewVal)
-        .addReg(Tmp).addImm(~uint32_t(0));
+        .addReg(Tmp).addImm(-1U << (32 - BitSize));
     else {
       // Use LCGR and add -1 to the result, which is more compact than
       // an XILF, XILH pair.