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Stay rational; don't assert trying to take the square root of a negative value.

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If it's negative, the loop is already proven to be infinite. Fixes PR13489!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161107 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky
2012-08-01 09:14:36 +00:00
parent 147d9e0511
commit 6ce2471806
2 changed files with 27 additions and 0 deletions
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6
lib/Analysis/ScalarEvolution.cpp
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@ -5370,6 +5370,12 @@ SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
SqrtTerm *= B;
SqrtTerm -= Four * (A * C);
if (SqrtTerm.isNegative()) {
// The loop is provably infinite.
const SCEV *CNC = SE.getCouldNotCompute();
return std::make_pair(CNC, CNC);
}
// Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
// integer value or else APInt::sqrt() will assert.
APInt SqrtVal(SqrtTerm.sqrt());