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When complicated expressions are broken down into subexpressions

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with multiplication by constants distributed through, occasionally
those subexpressions can include both x and -x. For now, if this
condition is discovered within LSR, just prune such cases away,
as they won't be profitable. This fixes a "zero allocated in a
base register" assertion failure.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96177 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-02-14 18:50:49 +00:00
parent 44de6823fc
commit ce947366ec
1 changed files with 8 additions and 2 deletions
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10
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -2012,8 +2012,14 @@ void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
F.BaseRegs.push_back(BaseReg);
}
if (Ops.size() > 1) {
F.BaseRegs.push_back(SE.getAddExpr(Ops));
(void)InsertFormula(LU, LUIdx, F);
const SCEV *Sum = SE.getAddExpr(Ops);
// TODO: If Sum is zero, it probably means ScalarEvolution missed an
// opportunity to fold something. For now, just ignore such cases
// rather than procede with zero in a register.
if (!Sum->isZero()) {
F.BaseRegs.push_back(Sum);
(void)InsertFormula(LU, LUIdx, F);
}
}
}