svn commit: r255076 - head/contrib/llvm/lib/Transforms/InstCombine

[Dimitry Andric]

Author: dim
Date: Fri Aug 30 18:29:25 2013
New Revision: 255076
URL: http://svnweb.freebsd.org/changeset/base/255076

Log:
  Pull in r189672 from upstream llvm trunk:
  
    InstCombine: Check for zero shift amounts before subtracting one
    causing integer overflow.
  
    PR17026. Also avoid undefined shifts and shift amounts larger than 64
    bits (those are always undef because we can't represent integer types
    that large).
  
  This should fix assertion failures when building the emulators/xmame
  port.
  
  Reported by:	bapt

Modified:
  head/contrib/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp

Modified: head/contrib/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
==============================================================================
--- head/contrib/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp	Fri Aug 30 17:47:53 2013	(r255075)
+++ head/contrib/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp	Fri Aug 30 18:29:25 2013	(r255076)
@@ -845,21 +845,26 @@ Value *InstCombiner::SimplifyDemandedUse
 Value *InstCombiner::SimplifyShrShlDemandedBits(Instruction *Shr,
   Instruction *Shl, APInt DemandedMask, APInt &KnownZero, APInt &KnownOne) {
 
-  unsigned ShlAmt = cast<ConstantInt>(Shl->getOperand(1))->getZExtValue();
-  unsigned ShrAmt = cast<ConstantInt>(Shr->getOperand(1))->getZExtValue();
+  const APInt &ShlOp1 = cast<ConstantInt>(Shl->getOperand(1))->getValue();
+  const APInt &ShrOp1 = cast<ConstantInt>(Shr->getOperand(1))->getValue();
+  if (!ShlOp1 || !ShrOp1)
+      return 0; // Noop.
+
+  Value *VarX = Shr->getOperand(0);
+  Type *Ty = VarX->getType();
+  unsigned BitWidth = Ty->getIntegerBitWidth();
+  if (ShlOp1.uge(BitWidth) || ShrOp1.uge(BitWidth))
+    return 0; // Undef.
+
+  unsigned ShlAmt = ShlOp1.getZExtValue();
+  unsigned ShrAmt = ShrOp1.getZExtValue();
 
   KnownOne.clearAllBits();
   KnownZero = APInt::getBitsSet(KnownZero.getBitWidth(), 0, ShlAmt-1);
   KnownZero &= DemandedMask;
 
-  if (ShlAmt == 0 || ShrAmt == 0)
-    return 0;
-
-  Value *VarX = Shr->getOperand(0);
-  Type *Ty = VarX->getType();
-
-  APInt BitMask1(APInt::getAllOnesValue(Ty->getIntegerBitWidth()));
-  APInt BitMask2(APInt::getAllOnesValue(Ty->getIntegerBitWidth()));
+  APInt BitMask1(APInt::getAllOnesValue(BitWidth));
+  APInt BitMask2(APInt::getAllOnesValue(BitWidth));
 
   bool isLshr = (Shr->getOpcode() == Instruction::LShr);
   BitMask1 = isLshr ? (BitMask1.lshr(ShrAmt) << ShlAmt) :