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-rw-r--r--lib/Analysis/ScalarEvolutionNormalization.cpp299
1 files changed, 78 insertions, 221 deletions
diff --git a/lib/Analysis/ScalarEvolutionNormalization.cpp b/lib/Analysis/ScalarEvolutionNormalization.cpp
index c1f9503816eea..2aaa4c1ae117f 100644
--- a/lib/Analysis/ScalarEvolutionNormalization.cpp
+++ b/lib/Analysis/ScalarEvolutionNormalization.cpp
@@ -12,243 +12,100 @@
//
//===----------------------------------------------------------------------===//
-#include "llvm/IR/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ScalarEvolutionNormalization.h"
using namespace llvm;
-/// IVUseShouldUsePostIncValue - We have discovered a "User" of an IV expression
-/// and now we need to decide whether the user should use the preinc or post-inc
-/// value. If this user should use the post-inc version of the IV, return true.
-///
-/// Choosing wrong here can break dominance properties (if we choose to use the
-/// post-inc value when we cannot) or it can end up adding extra live-ranges to
-/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
-/// should use the post-inc value).
-static bool IVUseShouldUsePostIncValue(Instruction *User, Value *Operand,
- const Loop *L, DominatorTree *DT) {
- // If the user is in the loop, use the preinc value.
- if (L->contains(User)) return false;
-
- BasicBlock *LatchBlock = L->getLoopLatch();
- if (!LatchBlock)
- return false;
-
- // Ok, the user is outside of the loop. If it is dominated by the latch
- // block, use the post-inc value.
- if (DT->dominates(LatchBlock, User->getParent()))
- return true;
-
- // There is one case we have to be careful of: PHI nodes. These little guys
- // can live in blocks that are not dominated by the latch block, but (since
- // their uses occur in the predecessor block, not the block the PHI lives in)
- // should still use the post-inc value. Check for this case now.
- PHINode *PN = dyn_cast<PHINode>(User);
- if (!PN || !Operand) return false; // not a phi, not dominated by latch block.
-
- // Look at all of the uses of Operand by the PHI node. If any use corresponds
- // to a block that is not dominated by the latch block, give up and use the
- // preincremented value.
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
- if (PN->getIncomingValue(i) == Operand &&
- !DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
- return false;
-
- // Okay, all uses of Operand by PN are in predecessor blocks that really are
- // dominated by the latch block. Use the post-incremented value.
- return true;
-}
+/// TransformKind - Different types of transformations that
+/// TransformForPostIncUse can do.
+enum TransformKind {
+ /// Normalize - Normalize according to the given loops.
+ Normalize,
+ /// Denormalize - Perform the inverse transform on the expression with the
+ /// given loop set.
+ Denormalize
+};
namespace {
-
-/// Hold the state used during post-inc expression transformation, including a
-/// map of transformed expressions.
-class PostIncTransform {
- TransformKind Kind;
- PostIncLoopSet &Loops;
- ScalarEvolution &SE;
- DominatorTree &DT;
-
- DenseMap<const SCEV*, const SCEV*> Transformed;
-
-public:
- PostIncTransform(TransformKind kind, PostIncLoopSet &loops,
- ScalarEvolution &se, DominatorTree &dt):
- Kind(kind), Loops(loops), SE(se), DT(dt) {}
-
- const SCEV *TransformSubExpr(const SCEV *S, Instruction *User,
- Value *OperandValToReplace);
-
-protected:
- const SCEV *TransformImpl(const SCEV *S, Instruction *User,
- Value *OperandValToReplace);
+struct NormalizeDenormalizeRewriter
+ : public SCEVRewriteVisitor<NormalizeDenormalizeRewriter> {
+ const TransformKind Kind;
+
+ // NB! Pred is a function_ref. Storing it here is okay only because
+ // we're careful about the lifetime of NormalizeDenormalizeRewriter.
+ const NormalizePredTy Pred;
+
+ NormalizeDenormalizeRewriter(TransformKind Kind, NormalizePredTy Pred,
+ ScalarEvolution &SE)
+ : SCEVRewriteVisitor<NormalizeDenormalizeRewriter>(SE), Kind(Kind),
+ Pred(Pred) {}
+ const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr);
};
-
} // namespace
-/// Implement post-inc transformation for all valid expression types.
-const SCEV *PostIncTransform::
-TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
-
- if (const SCEVCastExpr *X = dyn_cast<SCEVCastExpr>(S)) {
- const SCEV *O = X->getOperand();
- const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
- if (O != N)
- switch (S->getSCEVType()) {
- case scZeroExtend: return SE.getZeroExtendExpr(N, S->getType());
- case scSignExtend: return SE.getSignExtendExpr(N, S->getType());
- case scTruncate: return SE.getTruncateExpr(N, S->getType());
- default: llvm_unreachable("Unexpected SCEVCastExpr kind!");
- }
- return S;
- }
-
- if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
- // An addrec. This is the interesting part.
- SmallVector<const SCEV *, 8> Operands;
- const Loop *L = AR->getLoop();
- // The addrec conceptually uses its operands at loop entry.
- Instruction *LUser = &L->getHeader()->front();
- // Transform each operand.
- for (SCEVNAryExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
- I != E; ++I) {
- Operands.push_back(TransformSubExpr(*I, LUser, nullptr));
+const SCEV *
+NormalizeDenormalizeRewriter::visitAddRecExpr(const SCEVAddRecExpr *AR) {
+ SmallVector<const SCEV *, 8> Operands;
+
+ transform(AR->operands(), std::back_inserter(Operands),
+ [&](const SCEV *Op) { return visit(Op); });
+
+ // Conservatively use AnyWrap until/unless we need FlagNW.
+ const SCEV *Result =
+ SE.getAddRecExpr(Operands, AR->getLoop(), SCEV::FlagAnyWrap);
+ switch (Kind) {
+ 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 (Pred(AR)) {
+ const SCEV *TransformedStep = visit(AR->getStepRecurrence(SE));
+ Result = SE.getMinusSCEV(Result, TransformedStep);
}
- // Conservatively use AnyWrap until/unless we need FlagNW.
- const SCEV *Result = SE.getAddRecExpr(Operands, L, SCEV::FlagAnyWrap);
- switch (Kind) {
- case NormalizeAutodetect:
- // 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);
- Result = SE.getMinusSCEV(Result, TransformedStep);
- Loops.insert(L);
- }
-#if 0
- // This assert is conceptually correct, but ScalarEvolution currently
- // sometimes fails to canonicalize two equal SCEVs to exactly the same
- // form. It's possibly a pessimization when this happens, but it isn't a
- // correctness problem, so disable this assert for now.
- assert(S == TransformSubExpr(Result, User, OperandValToReplace) &&
- "SCEV normalization is not invertible!");
-#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),
- User, OperandValToReplace);
- Result = SE.getMinusSCEV(Result, TransformedStep);
- }
-#if 0
- // See the comment on the assert above.
- assert(S == TransformSubExpr(Result, User, OperandValToReplace) &&
- "SCEV normalization is not invertible!");
-#endif
- break;
- case Denormalize:
- // 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;
+ break;
+ case Denormalize:
+ // Here we want to normalize step expressions for the same reasons, as
+ // stated above.
+ if (Pred(AR)) {
+ const SCEV *TransformedStep = visit(AR->getStepRecurrence(SE));
+ Result = SE.getAddExpr(Result, TransformedStep);
}
- return Result;
- }
-
- if (const SCEVNAryExpr *X = dyn_cast<SCEVNAryExpr>(S)) {
- SmallVector<const SCEV *, 8> Operands;
- bool Changed = false;
- // Transform each operand.
- for (SCEVNAryExpr::op_iterator I = X->op_begin(), E = X->op_end();
- I != E; ++I) {
- const SCEV *O = *I;
- const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
- Changed |= N != O;
- Operands.push_back(N);
- }
- // If any operand actually changed, return a transformed result.
- if (Changed)
- switch (S->getSCEVType()) {
- case scAddExpr: return SE.getAddExpr(Operands);
- case scMulExpr: return SE.getMulExpr(Operands);
- case scSMaxExpr: return SE.getSMaxExpr(Operands);
- case scUMaxExpr: return SE.getUMaxExpr(Operands);
- default: llvm_unreachable("Unexpected SCEVNAryExpr kind!");
- }
- return S;
- }
-
- if (const SCEVUDivExpr *X = dyn_cast<SCEVUDivExpr>(S)) {
- const SCEV *LO = X->getLHS();
- const SCEV *RO = X->getRHS();
- const SCEV *LN = TransformSubExpr(LO, User, OperandValToReplace);
- const SCEV *RN = TransformSubExpr(RO, User, OperandValToReplace);
- if (LO != LN || RO != RN)
- return SE.getUDivExpr(LN, RN);
- return S;
+ break;
}
-
- llvm_unreachable("Unexpected SCEV kind!");
+ return Result;
}
-/// Manage recursive transformation across an expression DAG. Revisiting
-/// expressions would lead to exponential recursion.
-const SCEV *PostIncTransform::
-TransformSubExpr(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
-
- if (isa<SCEVConstant>(S) || isa<SCEVUnknown>(S))
- return S;
-
- const SCEV *Result = Transformed.lookup(S);
- if (Result)
- return Result;
+const SCEV *llvm::normalizeForPostIncUse(const SCEV *S,
+ const PostIncLoopSet &Loops,
+ ScalarEvolution &SE) {
+ auto Pred = [&](const SCEVAddRecExpr *AR) {
+ return Loops.count(AR->getLoop());
+ };
+ return NormalizeDenormalizeRewriter(Normalize, Pred, SE).visit(S);
+}
- Result = TransformImpl(S, User, OperandValToReplace);
- Transformed[S] = Result;
- return Result;
+const SCEV *llvm::normalizeForPostIncUseIf(const SCEV *S, NormalizePredTy Pred,
+ ScalarEvolution &SE) {
+ return NormalizeDenormalizeRewriter(Normalize, Pred, SE).visit(S);
}
-/// Top level driver for transforming an expression DAG into its requested
-/// post-inc form (either "Normalized" or "Denormalized").
-const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
- const SCEV *S,
- Instruction *User,
- Value *OperandValToReplace,
- PostIncLoopSet &Loops,
- ScalarEvolution &SE,
- DominatorTree &DT) {
- PostIncTransform Transform(Kind, Loops, SE, DT);
- return Transform.TransformSubExpr(S, User, OperandValToReplace);
+const SCEV *llvm::denormalizeForPostIncUse(const SCEV *S,
+ const PostIncLoopSet &Loops,
+ ScalarEvolution &SE) {
+ auto Pred = [&](const SCEVAddRecExpr *AR) {
+ return Loops.count(AR->getLoop());
+ };
+ return NormalizeDenormalizeRewriter(Denormalize, Pred, SE).visit(S);
}
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