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Fix an overly general check in SimplifyIndvar to handle useless phi cycles.
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
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@ -107,8 +107,8 @@ Value *SimplifyIndvar::foldIVUser(Instruction *UseInst, Instruction *IVOperand)
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// Attempt to fold a binary operator with constant operand.
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// e.g. ((I + 1) >> 2) => I >> 2
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if (IVOperand->getNumOperands() != 2 ||
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!isa<ConstantInt>(IVOperand->getOperand(1)))
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if (!isa<BinaryOperator>(IVOperand)
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|| !isa<ConstantInt>(IVOperand->getOperand(1)))
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return 0;
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IVSrc = IVOperand->getOperand(0);
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29
test/Transforms/IndVarSimplify/2011-11-17-selfphi.ll
Normal file
29
test/Transforms/IndVarSimplify/2011-11-17-selfphi.ll
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@ -0,0 +1,29 @@
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; RUN: opt < %s -indvars -S | FileCheck %s
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; PR11350: Check that SimplifyIndvar handles a cycle of useless self-phis.
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; CHECK: @test
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; CHECK-NOT: lcssa = phi
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define void @test() nounwind {
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entry:
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br label %for.cond.preheader
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for.cond.preheader: ; preds = %entry
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br label %for.cond.outer
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for.cond.outer: ; preds = %for.cond.preheader, %for.end
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%p_41.addr.0.ph = phi i32 [ %p_41.addr.1.lcssa, %for.end ], [ 1, %for.cond.preheader ]
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br label %for.cond
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for.cond:
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br i1 true, label %for.end, label %for.ph
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for.ph: ; preds = %for.cond4.preheader
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br label %for.end
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for.end:
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%p_41.addr.1.lcssa = phi i32 [ undef, %for.ph ], [ %p_41.addr.0.ph, %for.cond ]
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%p_68.lobit.i = lshr i32 %p_41.addr.1.lcssa, 31
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%cmp7 = icmp eq i32 %p_41.addr.1.lcssa, 0
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%conv8 = zext i1 %cmp7 to i32
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br label %for.cond.outer
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}
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