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Remove NormalizeAutodetect; NFC
It is cleaner to have a callback based system where the logic of whether an add recurrence is normalized or not lives on IVUsers. This is one step in a multi-step cleanup. llvm-svn: 300330
This commit is contained in:
Sanjoy Das
parent
07bb6fb214
commit
fdafc30cdf
@ -40,21 +40,15 @@
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namespace llvm {
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class Instruction;
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class DominatorTree;
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class Loop;
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class ScalarEvolution;
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class SCEV;
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class Value;
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/// TransformKind - Different types of transformations that
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/// TransformForPostIncUse can do.
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enum TransformKind {
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/// Normalize - Normalize according to the given loops.
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Normalize,
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/// NormalizeAutodetect - Detect post-inc opportunities on new expressions,
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/// update the given loop set, and normalize.
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NormalizeAutodetect,
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/// Denormalize - Perform the inverse transform on the expression with the
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/// given loop set.
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Denormalize
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@ -63,16 +57,13 @@ enum TransformKind {
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/// PostIncLoopSet - A set of loops.
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typedef SmallPtrSet<const Loop *, 2> PostIncLoopSet;
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typedef function_ref<bool(const SCEVAddRecExpr *)> NormalizePredTy;
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/// TransformForPostIncUse - Transform the given expression according to the
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/// given transformation kind.
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const SCEV *TransformForPostIncUse(TransformKind Kind,
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const SCEV *S,
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Instruction *User,
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Value *OperandValToReplace,
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PostIncLoopSet &Loops,
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ScalarEvolution &SE,
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DominatorTree &DT);
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const SCEV *TransformForPostIncUse(TransformKind Kind, const SCEV *S,
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Optional<NormalizePredTy> Pred,
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PostIncLoopSet &Loops, ScalarEvolution &SE);
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}
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#endif
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@ -117,6 +117,50 @@ static bool isSimplifiedLoopNest(BasicBlock *BB, const DominatorTree *DT,
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return true;
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}
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/// IVUseShouldUsePostIncValue - We have discovered a "User" of an IV expression
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/// and now we need to decide whether the user should use the preinc or post-inc
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/// value. If this user should use the post-inc version of the IV, return true.
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///
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/// Choosing wrong here can break dominance properties (if we choose to use the
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/// post-inc value when we cannot) or it can end up adding extra live-ranges to
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/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
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/// should use the post-inc value).
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static bool IVUseShouldUsePostIncValue(Instruction *User, Value *Operand,
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const Loop *L, DominatorTree *DT) {
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// If the user is in the loop, use the preinc value.
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if (L->contains(User))
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return false;
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BasicBlock *LatchBlock = L->getLoopLatch();
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if (!LatchBlock)
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return false;
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// Ok, the user is outside of the loop. If it is dominated by the latch
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// block, use the post-inc value.
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if (DT->dominates(LatchBlock, User->getParent()))
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return true;
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// There is one case we have to be careful of: PHI nodes. These little guys
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// can live in blocks that are not dominated by the latch block, but (since
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// their uses occur in the predecessor block, not the block the PHI lives in)
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// should still use the post-inc value. Check for this case now.
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PHINode *PN = dyn_cast<PHINode>(User);
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if (!PN || !Operand)
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return false; // not a phi, not dominated by latch block.
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// Look at all of the uses of Operand by the PHI node. If any use corresponds
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// to a block that is not dominated by the latch block, give up and use the
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// preincremented value.
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
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if (PN->getIncomingValue(i) == Operand &&
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!DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
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return false;
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// Okay, all uses of Operand by PN are in predecessor blocks that really are
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// dominated by the latch block. Use the post-incremented value.
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return true;
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}
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/// AddUsersImpl - Inspect the specified instruction. If it is a
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/// reducible SCEV, recursively add its users to the IVUsesByStride set and
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/// return true. Otherwise, return false.
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@ -207,19 +251,36 @@ bool IVUsers::AddUsersImpl(Instruction *I,
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// The regular return value here is discarded; instead of recording
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// it, we just recompute it when we need it.
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const SCEV *OriginalISE = ISE;
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ISE = TransformForPostIncUse(NormalizeAutodetect,
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ISE, User, I,
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NewUse.PostIncLoops,
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*SE, *DT);
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auto NormalizePred = [&](const SCEVAddRecExpr *AR) {
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// We only allow affine AddRecs to be normalized, otherwise we would not
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// be able to correctly denormalize.
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// e.g. {1,+,3,+,2} == {-2,+,1,+,2} + {3,+,2}
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// Normalized form: {-2,+,1,+,2}
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// Denormalized form: {1,+,3,+,2}
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//
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// However, denormalization would use a different step expression than
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// normalization (see getPostIncExpr), generating the wrong final
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// expression: {-2,+,1,+,2} + {1,+,2} => {-1,+,3,+,2}
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auto *L = AR->getLoop();
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bool Result =
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AR->isAffine() && IVUseShouldUsePostIncValue(User, I, L, DT);
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if (Result)
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NewUse.PostIncLoops.insert(L);
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return Result;
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};
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ISE = TransformForPostIncUse(Normalize, ISE,
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Optional<NormalizePredTy>(NormalizePred),
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NewUse.PostIncLoops, *SE);
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// PostIncNormalization effectively simplifies the expression under
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// pre-increment assumptions. Those assumptions (no wrapping) might not
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// hold for the post-inc value. Catch such cases by making sure the
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// transformation is invertible.
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if (OriginalISE != ISE) {
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const SCEV *DenormalizedISE =
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TransformForPostIncUse(Denormalize, ISE, User, I,
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NewUse.PostIncLoops, *SE, *DT);
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const SCEV *DenormalizedISE = TransformForPostIncUse(
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Denormalize, ISE, None, NewUse.PostIncLoops, *SE);
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// If we normalized the expression, but denormalization doesn't give the
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// original one, discard this user.
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@ -337,11 +398,9 @@ const SCEV *IVUsers::getReplacementExpr(const IVStrideUse &IU) const {
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/// getExpr - Return the expression for the use.
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const SCEV *IVUsers::getExpr(const IVStrideUse &IU) const {
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return
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TransformForPostIncUse(Normalize, getReplacementExpr(IU),
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IU.getUser(), IU.getOperandValToReplace(),
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const_cast<PostIncLoopSet &>(IU.getPostIncLoops()),
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*SE, *DT);
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return TransformForPostIncUse(
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Normalize, getReplacementExpr(IU), None,
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const_cast<PostIncLoopSet &>(IU.getPostIncLoops()), *SE);
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}
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static const SCEVAddRecExpr *findAddRecForLoop(const SCEV *S, const Loop *L) {
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@ -1268,8 +1268,8 @@ Value *SCEVExpander::expandAddRecExprLiterally(const SCEVAddRecExpr *S) {
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if (PostIncLoops.count(L)) {
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PostIncLoopSet Loops;
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Loops.insert(L);
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Normalized = cast<SCEVAddRecExpr>(TransformForPostIncUse(
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Normalize, S, nullptr, nullptr, Loops, SE, SE.DT));
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Normalized = cast<SCEVAddRecExpr>(
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TransformForPostIncUse(Normalize, S, None, Loops, SE));
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}
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// Strip off any non-loop-dominating component from the addrec start.
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@ -12,88 +12,41 @@
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/IR/Dominators.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/Analysis/ScalarEvolutionNormalization.h"
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using namespace llvm;
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/// IVUseShouldUsePostIncValue - We have discovered a "User" of an IV expression
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/// and now we need to decide whether the user should use the preinc or post-inc
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/// value. If this user should use the post-inc version of the IV, return true.
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///
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/// Choosing wrong here can break dominance properties (if we choose to use the
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/// post-inc value when we cannot) or it can end up adding extra live-ranges to
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/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
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/// should use the post-inc value).
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static bool IVUseShouldUsePostIncValue(Instruction *User, Value *Operand,
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const Loop *L, DominatorTree *DT) {
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// If the user is in the loop, use the preinc value.
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if (L->contains(User)) return false;
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BasicBlock *LatchBlock = L->getLoopLatch();
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if (!LatchBlock)
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return false;
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// Ok, the user is outside of the loop. If it is dominated by the latch
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// block, use the post-inc value.
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if (DT->dominates(LatchBlock, User->getParent()))
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return true;
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// There is one case we have to be careful of: PHI nodes. These little guys
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// can live in blocks that are not dominated by the latch block, but (since
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// their uses occur in the predecessor block, not the block the PHI lives in)
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// should still use the post-inc value. Check for this case now.
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PHINode *PN = dyn_cast<PHINode>(User);
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if (!PN || !Operand) return false; // not a phi, not dominated by latch block.
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// Look at all of the uses of Operand by the PHI node. If any use corresponds
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// to a block that is not dominated by the latch block, give up and use the
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// preincremented value.
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
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if (PN->getIncomingValue(i) == Operand &&
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!DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
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return false;
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// Okay, all uses of Operand by PN are in predecessor blocks that really are
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// dominated by the latch block. Use the post-incremented value.
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return true;
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}
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namespace {
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/// Hold the state used during post-inc expression transformation, including a
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/// map of transformed expressions.
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class PostIncTransform {
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TransformKind Kind;
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Optional<NormalizePredTy> Pred;
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PostIncLoopSet &Loops;
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ScalarEvolution &SE;
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DominatorTree &DT;
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DenseMap<const SCEV*, const SCEV*> Transformed;
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public:
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PostIncTransform(TransformKind kind, PostIncLoopSet &loops,
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ScalarEvolution &se, DominatorTree &dt):
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Kind(kind), Loops(loops), SE(se), DT(dt) {}
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PostIncTransform(TransformKind kind, Optional<NormalizePredTy> Pred,
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PostIncLoopSet &loops, ScalarEvolution &se)
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: Kind(kind), Pred(Pred), Loops(loops), SE(se) {}
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const SCEV *TransformSubExpr(const SCEV *S, Instruction *User,
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Value *OperandValToReplace);
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const SCEV *TransformSubExpr(const SCEV *S);
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protected:
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const SCEV *TransformImpl(const SCEV *S, Instruction *User,
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Value *OperandValToReplace);
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const SCEV *TransformImpl(const SCEV *S);
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};
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} // namespace
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/// Implement post-inc transformation for all valid expression types.
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const SCEV *PostIncTransform::
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TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
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const SCEV *PostIncTransform::TransformImpl(const SCEV *S) {
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if (const SCEVCastExpr *X = dyn_cast<SCEVCastExpr>(S)) {
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const SCEV *O = X->getOperand();
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const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
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const SCEV *N = TransformSubExpr(O);
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if (O != N)
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switch (S->getSCEVType()) {
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case scZeroExtend: return SE.getZeroExtendExpr(N, S->getType());
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@ -108,44 +61,13 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
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// An addrec. This is the interesting part.
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SmallVector<const SCEV *, 8> Operands;
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const Loop *L = AR->getLoop();
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// The addrec conceptually uses its operands at loop entry.
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Instruction *LUser = &L->getHeader()->front();
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transform(
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AR->operands(), std::back_inserter(Operands),
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[&](const SCEV *Op) { return TransformSubExpr(Op, LUser, nullptr); });
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transform(AR->operands(), std::back_inserter(Operands),
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[&](const SCEV *Op) { return TransformSubExpr(Op); });
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// Conservatively use AnyWrap until/unless we need FlagNW.
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const SCEV *Result = SE.getAddRecExpr(Operands, L, SCEV::FlagAnyWrap);
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switch (Kind) {
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case NormalizeAutodetect:
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// Normalize this SCEV by subtracting the expression for the final step.
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// We only allow affine AddRecs to be normalized, otherwise we would not
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// be able to correctly denormalize.
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// e.g. {1,+,3,+,2} == {-2,+,1,+,2} + {3,+,2}
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// Normalized form: {-2,+,1,+,2}
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// Denormalized form: {1,+,3,+,2}
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//
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// However, denormalization would use a different step expression than
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// normalization (see getPostIncExpr), generating the wrong final
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// expression: {-2,+,1,+,2} + {1,+,2} => {-1,+,3,+,2}
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if (AR->isAffine() &&
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IVUseShouldUsePostIncValue(User, OperandValToReplace, L, &DT)) {
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const SCEV *TransformedStep =
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TransformSubExpr(AR->getStepRecurrence(SE),
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User, OperandValToReplace);
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Result = SE.getMinusSCEV(Result, TransformedStep);
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Loops.insert(L);
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}
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#if 0
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// This assert is conceptually correct, but ScalarEvolution currently
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// sometimes fails to canonicalize two equal SCEVs to exactly the same
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// form. It's possibly a pessimization when this happens, but it isn't a
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// correctness problem, so disable this assert for now.
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assert(S == TransformSubExpr(Result, User, OperandValToReplace) &&
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"SCEV normalization is not invertible!");
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#endif
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break;
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case Normalize:
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// We want to normalize step expression, because otherwise we might not be
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// able to denormalize to the original expression.
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@ -161,10 +83,9 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
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// (100 /u {1,+,1}<%bb16>)}<%bb25>
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// Note that the initial value changes after normalization +
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// denormalization, which isn't correct.
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if (Loops.count(L)) {
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if ((Pred && (*Pred)(AR)) || (!Pred && Loops.count(L))) {
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const SCEV *TransformedStep =
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TransformSubExpr(AR->getStepRecurrence(SE),
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User, OperandValToReplace);
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TransformSubExpr(AR->getStepRecurrence(SE));
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Result = SE.getMinusSCEV(Result, TransformedStep);
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}
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#if 0
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@ -178,8 +99,7 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
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// stated above.
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if (Loops.count(L)) {
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const SCEV *TransformedStep =
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TransformSubExpr(AR->getStepRecurrence(SE),
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User, OperandValToReplace);
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TransformSubExpr(AR->getStepRecurrence(SE));
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Result = SE.getAddExpr(Result, TransformedStep);
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}
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break;
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@ -194,7 +114,7 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
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for (SCEVNAryExpr::op_iterator I = X->op_begin(), E = X->op_end();
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I != E; ++I) {
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const SCEV *O = *I;
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const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
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const SCEV *N = TransformSubExpr(O);
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Changed |= N != O;
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Operands.push_back(N);
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}
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@ -213,8 +133,8 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
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if (const SCEVUDivExpr *X = dyn_cast<SCEVUDivExpr>(S)) {
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const SCEV *LO = X->getLHS();
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const SCEV *RO = X->getRHS();
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const SCEV *LN = TransformSubExpr(LO, User, OperandValToReplace);
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const SCEV *RN = TransformSubExpr(RO, User, OperandValToReplace);
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const SCEV *LN = TransformSubExpr(LO);
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const SCEV *RN = TransformSubExpr(RO);
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if (LO != LN || RO != RN)
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return SE.getUDivExpr(LN, RN);
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return S;
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@ -225,9 +145,7 @@ TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
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/// Manage recursive transformation across an expression DAG. Revisiting
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/// expressions would lead to exponential recursion.
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const SCEV *PostIncTransform::
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TransformSubExpr(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
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const SCEV *PostIncTransform::TransformSubExpr(const SCEV *S) {
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if (isa<SCEVConstant>(S) || isa<SCEVUnknown>(S))
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return S;
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@ -235,20 +153,17 @@ TransformSubExpr(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
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if (Result)
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return Result;
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Result = TransformImpl(S, User, OperandValToReplace);
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Result = TransformImpl(S);
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Transformed[S] = Result;
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return Result;
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}
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/// Top level driver for transforming an expression DAG into its requested
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/// post-inc form (either "Normalized" or "Denormalized").
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const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
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const SCEV *S,
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Instruction *User,
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Value *OperandValToReplace,
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const SCEV *llvm::TransformForPostIncUse(TransformKind Kind, const SCEV *S,
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Optional<NormalizePredTy> Pred,
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PostIncLoopSet &Loops,
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ScalarEvolution &SE,
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DominatorTree &DT) {
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PostIncTransform Transform(Kind, Loops, SE, DT);
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return Transform.TransformSubExpr(S, User, OperandValToReplace);
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ScalarEvolution &SE) {
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PostIncTransform Transform(Kind, Pred, Loops, SE);
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return Transform.TransformSubExpr(S);
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}
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@ -3160,8 +3160,7 @@ void LSRInstance::CollectFixupsAndInitialFormulae() {
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if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
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// S is normalized, so normalize N before folding it into S
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// to keep the result normalized.
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N = TransformForPostIncUse(Normalize, N, CI, nullptr,
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TmpPostIncLoops, SE, DT);
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N = TransformForPostIncUse(Normalize, N, None, TmpPostIncLoops, SE);
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Kind = LSRUse::ICmpZero;
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S = SE.getMinusSCEV(N, S);
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}
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@ -4800,10 +4799,7 @@ Value *LSRInstance::Expand(const LSRUse &LU,
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||||
|
||||
// If we're expanding for a post-inc user, make the post-inc adjustment.
|
||||
PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
|
||||
Reg = TransformForPostIncUse(Denormalize, Reg,
|
||||
LF.UserInst, LF.OperandValToReplace,
|
||||
Loops, SE, DT);
|
||||
|
||||
Reg = TransformForPostIncUse(Denormalize, Reg, None, Loops, SE);
|
||||
Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
|
||||
}
|
||||
|
||||
@ -4814,9 +4810,7 @@ Value *LSRInstance::Expand(const LSRUse &LU,
|
||||
|
||||
// If we're expanding for a post-inc user, make the post-inc adjustment.
|
||||
PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
|
||||
ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
|
||||
LF.UserInst, LF.OperandValToReplace,
|
||||
Loops, SE, DT);
|
||||
ScaledS = TransformForPostIncUse(Denormalize, ScaledS, None, Loops, SE);
|
||||
|
||||
if (LU.Kind == LSRUse::ICmpZero) {
|
||||
// Expand ScaleReg as if it was part of the base regs.
|
||||
|
||||
Loading…
Reference in New Issue
Block a user