[llvm-commits] [llvm] r52003 - /llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp

[Zhou Sheng]

Author: sheng
Date: Thu Jun  5 09:23:44 2008
New Revision: 52003

URL: http://llvm.org/viewvc/llvm-project?rev=52003&view=rev
Log:
If BitWidth equals to ShtAmt, the RHSKnownZero[BitWidth-ShiftAmt-1] will
crash the opt. Just fix this.

Test case in llvm/test/Transforms/InstCombine/2008-06-05-ashr-crash.ll

Modified:
    llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=52003&r1=52002&r2=52003&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Thu Jun  5 09:23:44 2008
@@ -1236,7 +1236,7 @@
         
       // If the input sign bit is known to be zero, or if none of the top bits
       // are demanded, turn this into an unsigned shift right.
-      if (RHSKnownZero[BitWidth-ShiftAmt-1] || 
+      if (BitWidth == ShiftAmt || RHSKnownZero[BitWidth-ShiftAmt-1] || 
           (HighBits & ~DemandedMask) == HighBits) {
         // Perform the logical shift right.
         Value *NewVal = BinaryOperator::CreateLShr(