diff options
Diffstat (limited to 'contrib/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp')
| -rw-r--r-- | contrib/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/contrib/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp b/contrib/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp index dd2ed4f..f110616 100644 --- a/contrib/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp +++ b/contrib/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp @@ -119,11 +119,19 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) { const SCEV *Result = SE.getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); switch (Kind) { case NormalizeAutodetect: - if (IVUseShouldUsePostIncValue(User, OperandValToReplace, L, &DT)) { - const SCEV *TransformedStep = - TransformSubExpr(AR->getStepRecurrence(SE), - User, OperandValToReplace); - Result = SE.getMinusSCEV(Result, TransformedStep); + // Normalize this SCEV by subtracting the expression for the final step. + // We only allow affine AddRecs to be normalized, otherwise we would not + // be able to correctly denormalize. + // e.g. {1,+,3,+,2} == {-2,+,1,+,2} + {3,+,2} + // Normalized form: {-2,+,1,+,2} + // Denormalized form: {1,+,3,+,2} + // + // However, denormalization would use the a different step expression than + // normalization (see getPostIncExpr), generating the wrong final + // expression: {-2,+,1,+,2} + {1,+,2} => {-1,+,3,+,2} + if (AR->isAffine() && + IVUseShouldUsePostIncValue(User, OperandValToReplace, L, &DT)) { + Result = SE.getMinusSCEV(Result, AR->getStepRecurrence(SE)); Loops.insert(L); } #if 0 |
