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Fix an overly general check in SimplifyIndvar to handle useless phi cycles.

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The right way to check for a binary operation is
cast<BinaryOperator>. The original check: cast<Instruction> &&
numOperands() == 2 would match phi "instructions", leading to an
infinite loop in extreme corner case: a useless phi with operands
[self, constant] that prior optimization passes failed to remove,
being used in the loop by another useless phi, in turn being used by an
lshr or udiv.

Fixes PR11350: runaway iteration assertion.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144935 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick
2011-11-17 23:36:35 +00:00
parent 7cf2a04361
commit 4f3052403c
2 changed files with 31 additions and 2 deletions
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4
lib/Transforms/Utils/SimplifyIndVar.cpp
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@@ -107,8 +107,8 @@ Value *SimplifyIndvar::foldIVUser(Instruction *UseInst, Instruction *IVOperand)
// Attempt to fold a binary operator with constant operand.
// e.g. ((I + 1) >> 2) => I >> 2
if (IVOperand->getNumOperands() != 2 ||
!isa<ConstantInt>(IVOperand->getOperand(1)))
if (!isa<BinaryOperator>(IVOperand)
|| !isa<ConstantInt>(IVOperand->getOperand(1)))
return 0;
IVSrc = IVOperand->getOperand(0);