//
//===----------------------------------------------------------------------===//
-#include "llvm/Analysis/Dominators.h"
+#include "llvm/IR/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ScalarEvolutionNormalization.h"
// Transform each operand.
for (SCEVNAryExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
I != E; ++I) {
- Operands.push_back(TransformSubExpr(*I, LUser, 0));
+ Operands.push_back(TransformSubExpr(*I, LUser, nullptr));
}
// Conservatively use AnyWrap until/unless we need FlagNW.
const SCEV *Result = SE.getAddRecExpr(Operands, L, SCEV::FlagAnyWrap);
switch (Kind) {
- default: llvm_unreachable("Unexpected transform name!");
case NormalizeAutodetect:
- if (IVUseShouldUsePostIncValue(User, OperandValToReplace, L, &DT)) {
+ // 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 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)) {
const SCEV *TransformedStep =
TransformSubExpr(AR->getStepRecurrence(SE),
User, OperandValToReplace);
#endif
break;
case Normalize:
+ // We want to normalize step expression, because otherwise we might not be
+ // able to denormalize to the original expression.
+ //
+ // Here is an example what will happen if we don't normalize step:
+ // ORIGINAL ISE:
+ // {(100 /u {1,+,1}<%bb16>),+,(100 /u {1,+,1}<%bb16>)}<%bb25>
+ // NORMALIZED ISE:
+ // {((-1 * (100 /u {1,+,1}<%bb16>)) + (100 /u {0,+,1}<%bb16>)),+,
+ // (100 /u {0,+,1}<%bb16>)}<%bb25>
+ // DENORMALIZED BACK ISE:
+ // {((2 * (100 /u {1,+,1}<%bb16>)) + (-1 * (100 /u {2,+,1}<%bb16>))),+,
+ // (100 /u {1,+,1}<%bb16>)}<%bb25>
+ // Note that the initial value changes after normalization +
+ // denormalization, which isn't correct.
if (Loops.count(L)) {
const SCEV *TransformedStep =
TransformSubExpr(AR->getStepRecurrence(SE),
#endif
break;
case Denormalize:
- if (Loops.count(L))
- Result = cast<SCEVAddRecExpr>(Result)->getPostIncExpr(SE);
+ // Here we want to normalize step expressions for the same reasons, as
+ // stated above.
+ if (Loops.count(L)) {
+ const SCEV *TransformedStep =
+ TransformSubExpr(AR->getStepRecurrence(SE),
+ User, OperandValToReplace);
+ Result = SE.getAddExpr(Result, TransformedStep);
+ }
break;
}
return Result;
}
llvm_unreachable("Unexpected SCEV kind!");
- return 0;
}
/// Manage recursive transformation across an expression DAG. Revisiting
if (isa<SCEVConstant>(S) || isa<SCEVUnknown>(S))
return S;
- const SCEV *&ExprRef = Transformed[S];
- if (ExprRef)
- return ExprRef;
+ const SCEV *Result = Transformed.lookup(S);
+ if (Result)
+ return Result;
- ExprRef = TransformImpl(S, User, OperandValToReplace);
- return ExprRef;
+ Result = TransformImpl(S, User, OperandValToReplace);
+ Transformed[S] = Result;
+ return Result;
}
/// Top level driver for transforming an expression DAG into its requested
-/// post-inc form (either "Normalized" or "Denormalized".
+/// post-inc form (either "Normalized" or "Denormalized").
const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
const SCEV *S,
Instruction *User,