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-rw-r--r--llvm/lib/Transforms/Scalar/IndVarSimplify.cpp272
1 files changed, 7 insertions, 265 deletions
diff --git a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
index 490617a0c8c..5566ecca6a1 100644
--- a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -33,7 +33,6 @@
#include "llvm/LLVMContext.h"
#include "llvm/Type.h"
#include "llvm/Analysis/Dominators.h"
-#include "llvm/Analysis/IVUsers.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
@@ -50,18 +49,12 @@
#include "llvm/ADT/Statistic.h"
using namespace llvm;
-STATISTIC(NumRemoved , "Number of aux indvars removed");
STATISTIC(NumWidened , "Number of indvars widened");
-STATISTIC(NumInserted , "Number of canonical indvars added");
STATISTIC(NumReplaced , "Number of exit values replaced");
STATISTIC(NumLFTR , "Number of loop exit tests replaced");
STATISTIC(NumElimExt , "Number of IV sign/zero extends eliminated");
STATISTIC(NumElimIV , "Number of congruent IVs eliminated");
-static cl::opt<bool> EnableIVRewrite(
- "enable-iv-rewrite", cl::Hidden,
- cl::desc("Enable canonical induction variable rewriting"));
-
// Trip count verification can be enabled by default under NDEBUG if we
// implement a strong expression equivalence checker in SCEV. Until then, we
// use the verify-indvars flag, which may assert in some cases.
@@ -71,7 +64,6 @@ static cl::opt<bool> VerifyIndvars(
namespace {
class IndVarSimplify : public LoopPass {
- IVUsers *IU;
LoopInfo *LI;
ScalarEvolution *SE;
DominatorTree *DT;
@@ -82,7 +74,7 @@ namespace {
public:
static char ID; // Pass identification, replacement for typeid
- IndVarSimplify() : LoopPass(ID), IU(0), LI(0), SE(0), DT(0), TD(0),
+ IndVarSimplify() : LoopPass(ID), LI(0), SE(0), DT(0), TD(0),
Changed(false) {
initializeIndVarSimplifyPass(*PassRegistry::getPassRegistry());
}
@@ -95,13 +87,9 @@ namespace {
AU.addRequired<ScalarEvolution>();
AU.addRequiredID(LoopSimplifyID);
AU.addRequiredID(LCSSAID);
- if (EnableIVRewrite)
- AU.addRequired<IVUsers>();
AU.addPreserved<ScalarEvolution>();
AU.addPreservedID(LoopSimplifyID);
AU.addPreservedID(LCSSAID);
- if (EnableIVRewrite)
- AU.addPreserved<IVUsers>();
AU.setPreservesCFG();
}
@@ -119,8 +107,6 @@ namespace {
void RewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter);
- void RewriteIVExpressions(Loop *L, SCEVExpander &Rewriter);
-
Value *LinearFunctionTestReplace(Loop *L, const SCEV *BackedgeTakenCount,
PHINode *IndVar, SCEVExpander &Rewriter);
@@ -136,7 +122,6 @@ INITIALIZE_PASS_DEPENDENCY(LoopInfo)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
INITIALIZE_PASS_DEPENDENCY(LCSSA)
-INITIALIZE_PASS_DEPENDENCY(IVUsers)
INITIALIZE_PASS_END(IndVarSimplify, "indvars",
"Induction Variable Simplification", false, false)
@@ -448,13 +433,6 @@ void IndVarSimplify::HandleFloatingPointIV(Loop *L, PHINode *PN) {
PN->replaceAllUsesWith(Conv);
RecursivelyDeleteTriviallyDeadInstructions(PN);
}
-
- // Add a new IVUsers entry for the newly-created integer PHI.
- if (IU) {
- SmallPtrSet<Loop*, 16> SimplifiedLoopNests;
- IU->AddUsersIfInteresting(NewPHI, SimplifiedLoopNests);
- }
-
Changed = true;
}
@@ -600,124 +578,6 @@ void IndVarSimplify::RewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) {
}
//===----------------------------------------------------------------------===//
-// Rewrite IV users based on a canonical IV.
-// Only for use with -enable-iv-rewrite.
-//===----------------------------------------------------------------------===//
-
-/// FIXME: It is an extremely bad idea to indvar substitute anything more
-/// complex than affine induction variables. Doing so will put expensive
-/// polynomial evaluations inside of the loop, and the str reduction pass
-/// currently can only reduce affine polynomials. For now just disable
-/// indvar subst on anything more complex than an affine addrec, unless
-/// it can be expanded to a trivial value.
-static bool isSafe(const SCEV *S, const Loop *L, ScalarEvolution *SE) {
- // Loop-invariant values are safe.
- if (SE->isLoopInvariant(S, L)) return true;
-
- // Affine addrecs are safe. Non-affine are not, because LSR doesn't know how
- // to transform them into efficient code.
- if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
- return AR->isAffine();
-
- // An add is safe it all its operands are safe.
- if (const SCEVCommutativeExpr *Commutative
- = dyn_cast<SCEVCommutativeExpr>(S)) {
- for (SCEVCommutativeExpr::op_iterator I = Commutative->op_begin(),
- E = Commutative->op_end(); I != E; ++I)
- if (!isSafe(*I, L, SE)) return false;
- return true;
- }
-
- // A cast is safe if its operand is.
- if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
- return isSafe(C->getOperand(), L, SE);
-
- // A udiv is safe if its operands are.
- if (const SCEVUDivExpr *UD = dyn_cast<SCEVUDivExpr>(S))
- return isSafe(UD->getLHS(), L, SE) &&
- isSafe(UD->getRHS(), L, SE);
-
- // SCEVUnknown is always safe.
- if (isa<SCEVUnknown>(S))
- return true;
-
- // Nothing else is safe.
- return false;
-}
-
-void IndVarSimplify::RewriteIVExpressions(Loop *L, SCEVExpander &Rewriter) {
- // Rewrite all induction variable expressions in terms of the canonical
- // induction variable.
- //
- // If there were induction variables of other sizes or offsets, manually
- // add the offsets to the primary induction variable and cast, avoiding
- // the need for the code evaluation methods to insert induction variables
- // of different sizes.
- for (IVUsers::iterator UI = IU->begin(), E = IU->end(); UI != E; ++UI) {
- Value *Op = UI->getOperandValToReplace();
- Type *UseTy = Op->getType();
- Instruction *User = UI->getUser();
-
- // Compute the final addrec to expand into code.
- const SCEV *AR = IU->getReplacementExpr(*UI);
-
- // Evaluate the expression out of the loop, if possible.
- if (!L->contains(UI->getUser())) {
- const SCEV *ExitVal = SE->getSCEVAtScope(AR, L->getParentLoop());
- if (SE->isLoopInvariant(ExitVal, L))
- AR = ExitVal;
- }
-
- // FIXME: It is an extremely bad idea to indvar substitute anything more
- // complex than affine induction variables. Doing so will put expensive
- // polynomial evaluations inside of the loop, and the str reduction pass
- // currently can only reduce affine polynomials. For now just disable
- // indvar subst on anything more complex than an affine addrec, unless
- // it can be expanded to a trivial value.
- if (!isSafe(AR, L, SE))
- continue;
-
- // Determine the insertion point for this user. By default, insert
- // immediately before the user. The SCEVExpander class will automatically
- // hoist loop invariants out of the loop. For PHI nodes, there may be
- // multiple uses, so compute the nearest common dominator for the
- // incoming blocks.
- Instruction *InsertPt = getInsertPointForUses(User, Op, DT);
-
- // Now expand it into actual Instructions and patch it into place.
- Value *NewVal = Rewriter.expandCodeFor(AR, UseTy, InsertPt);
-
- DEBUG(dbgs() << "INDVARS: Rewrote IV '" << *AR << "' " << *Op << '\n'
- << " into = " << *NewVal << "\n");
-
- if (!isValidRewrite(Op, NewVal)) {
- DeadInsts.push_back(NewVal);
- continue;
- }
- // Inform ScalarEvolution that this value is changing. The change doesn't
- // affect its value, but it does potentially affect which use lists the
- // value will be on after the replacement, which affects ScalarEvolution's
- // ability to walk use lists and drop dangling pointers when a value is
- // deleted.
- SE->forgetValue(User);
-
- // Patch the new value into place.
- if (Op->hasName())
- NewVal->takeName(Op);
- if (Instruction *NewValI = dyn_cast<Instruction>(NewVal))
- NewValI->setDebugLoc(User->getDebugLoc());
- User->replaceUsesOfWith(Op, NewVal);
- UI->setOperandValToReplace(NewVal);
-
- ++NumRemoved;
- Changed = true;
-
- // The old value may be dead now.
- DeadInsts.push_back(Op);
- }
-}
-
-//===----------------------------------------------------------------------===//
// IV Widening - Extend the width of an IV to cover its widest uses.
//===----------------------------------------------------------------------===//
@@ -1262,9 +1122,6 @@ static bool isHighCostExpansion(const SCEV *S, BranchInst *BI,
}
}
- if (EnableIVRewrite)
- return false;
-
// Recurse past add expressions, which commonly occur in the
// BackedgeTakenCount. They may already exist in program code, and if not,
// they are not too expensive rematerialize.
@@ -1321,36 +1178,6 @@ static bool canExpandBackedgeTakenCount(Loop *L, ScalarEvolution *SE) {
return true;
}
-/// getBackedgeIVType - Get the widest type used by the loop test after peeking
-/// through Truncs.
-///
-/// TODO: Unnecessary when ForceLFTR is removed.
-static Type *getBackedgeIVType(Loop *L) {
- if (!L->getExitingBlock())
- return 0;
-
- // Can't rewrite non-branch yet.
- BranchInst *BI = dyn_cast<BranchInst>(L->getExitingBlock()->getTerminator());
- if (!BI)
- return 0;
-
- ICmpInst *Cond = dyn_cast<ICmpInst>(BI->getCondition());
- if (!Cond)
- return 0;
-
- Type *Ty = 0;
- for(User::op_iterator OI = Cond->op_begin(), OE = Cond->op_end();
- OI != OE; ++OI) {
- assert((!Ty || Ty == (*OI)->getType()) && "bad icmp operand types");
- TruncInst *Trunc = dyn_cast<TruncInst>(*OI);
- if (!Trunc)
- continue;
-
- return Trunc->getSrcTy();
- }
- return Ty;
-}
-
/// getLoopPhiForCounter - Return the loop header phi IFF IncV adds a loop
/// invariant value to the phi.
static PHINode *getLoopPhiForCounter(Value *IncV, Loop *L, DominatorTree *DT) {
@@ -1619,8 +1446,7 @@ LinearFunctionTestReplace(Loop *L,
// LFTR can ignore IV overflow and truncate to the width of
// BECount. This avoids materializing the add(zext(add)) expression.
- Type *CntTy = !EnableIVRewrite ?
- BackedgeTakenCount->getType() : IndVar->getType();
+ Type *CntTy = BackedgeTakenCount->getType();
const SCEV *IVCount = BackedgeTakenCount;
@@ -1805,8 +1631,6 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
if (!L->isLoopSimplifyForm())
return false;
- if (EnableIVRewrite)
- IU = &getAnalysis<IVUsers>();
LI = &getAnalysis<LoopInfo>();
SE = &getAnalysis<ScalarEvolution>();
DT = &getAnalysis<DominatorTree>();
@@ -1833,10 +1657,8 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
// attempt to avoid evaluating SCEVs for sign/zero extend operations until
// other expressions involving loop IVs have been evaluated. This helps SCEV
// set no-wrap flags before normalizing sign/zero extension.
- if (!EnableIVRewrite) {
- Rewriter.disableCanonicalMode();
- SimplifyAndExtend(L, Rewriter, LPM);
- }
+ Rewriter.disableCanonicalMode();
+ SimplifyAndExtend(L, Rewriter, LPM);
// Check to see if this loop has a computable loop-invariant execution count.
// If so, this means that we can compute the final value of any expressions
@@ -1847,83 +1669,17 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
if (!isa<SCEVCouldNotCompute>(BackedgeTakenCount))
RewriteLoopExitValues(L, Rewriter);
- // Eliminate redundant IV users.
- if (EnableIVRewrite)
- Changed |= simplifyIVUsers(IU, SE, &LPM, DeadInsts);
-
// Eliminate redundant IV cycles.
- if (!EnableIVRewrite)
- NumElimIV += Rewriter.replaceCongruentIVs(L, DT, DeadInsts);
+ NumElimIV += Rewriter.replaceCongruentIVs(L, DT, DeadInsts);
// Compute the type of the largest recurrence expression, and decide whether
// a canonical induction variable should be inserted.
- Type *LargestType = 0;
- bool NeedCannIV = false;
bool ExpandBECount = canExpandBackedgeTakenCount(L, SE);
- if (EnableIVRewrite && ExpandBECount) {
- // If we have a known trip count and a single exit block, we'll be
- // rewriting the loop exit test condition below, which requires a
- // canonical induction variable.
- NeedCannIV = true;
- Type *Ty = BackedgeTakenCount->getType();
- if (!EnableIVRewrite) {
- // In this mode, SimplifyIVUsers may have already widened the IV used by
- // the backedge test and inserted a Trunc on the compare's operand. Get
- // the wider type to avoid creating a redundant narrow IV only used by the
- // loop test.
- LargestType = getBackedgeIVType(L);
- }
- if (!LargestType ||
- SE->getTypeSizeInBits(Ty) >
- SE->getTypeSizeInBits(LargestType))
- LargestType = SE->getEffectiveSCEVType(Ty);
- }
- if (EnableIVRewrite) {
- for (IVUsers::const_iterator I = IU->begin(), E = IU->end(); I != E; ++I) {
- NeedCannIV = true;
- Type *Ty =
- SE->getEffectiveSCEVType(I->getOperandValToReplace()->getType());
- if (!LargestType ||
- SE->getTypeSizeInBits(Ty) >
- SE->getTypeSizeInBits(LargestType))
- LargestType = Ty;
- }
- }
// Now that we know the largest of the induction variable expressions
// in this loop, insert a canonical induction variable of the largest size.
PHINode *IndVar = 0;
- if (NeedCannIV) {
- // Check to see if the loop already has any canonical-looking induction
- // variables. If any are present and wider than the planned canonical
- // induction variable, temporarily remove them, so that the Rewriter
- // doesn't attempt to reuse them.
- SmallVector<PHINode *, 2> OldCannIVs;
- while (PHINode *OldCannIV = L->getCanonicalInductionVariable()) {
- if (SE->getTypeSizeInBits(OldCannIV->getType()) >
- SE->getTypeSizeInBits(LargestType))
- OldCannIV->removeFromParent();
- else
- break;
- OldCannIVs.push_back(OldCannIV);
- }
-
- IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L, LargestType);
-
- ++NumInserted;
- Changed = true;
- DEBUG(dbgs() << "INDVARS: New CanIV: " << *IndVar << '\n');
-
- // Now that the official induction variable is established, reinsert
- // any old canonical-looking variables after it so that the IR remains
- // consistent. They will be deleted as part of the dead-PHI deletion at
- // the end of the pass.
- while (!OldCannIVs.empty()) {
- PHINode *OldCannIV = OldCannIVs.pop_back_val();
- OldCannIV->insertBefore(L->getHeader()->getFirstInsertionPt());
- }
- }
- else if (!EnableIVRewrite && ExpandBECount && needsLFTR(L, DT)) {
+ if (ExpandBECount && needsLFTR(L, DT)) {
IndVar = FindLoopCounter(L, BackedgeTakenCount, SE, DT, TD);
}
// If we have a trip count expression, rewrite the loop's exit condition
@@ -1943,9 +1699,6 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
NewICmp =
LinearFunctionTestReplace(L, BackedgeTakenCount, IndVar, Rewriter);
}
- // Rewrite IV-derived expressions.
- if (EnableIVRewrite)
- RewriteIVExpressions(L, Rewriter);
// Clear the rewriter cache, because values that are in the rewriter's cache
// can be deleted in the loop below, causing the AssertingVH in the cache to
@@ -1965,16 +1718,6 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
// loop may be sunk below the loop to reduce register pressure.
SinkUnusedInvariants(L);
- // For completeness, inform IVUsers of the IV use in the newly-created
- // loop exit test instruction.
- if (IU && NewICmp) {
- ICmpInst *NewICmpInst = dyn_cast<ICmpInst>(NewICmp);
- if (NewICmpInst) {
- SmallPtrSet<Loop*, 16> SimplifiedLoopNests;
- IU->AddUsersIfInteresting(cast<Instruction>(NewICmpInst->getOperand(0)),
- SimplifiedLoopNests);
- }
- }
// Clean up dead instructions.
Changed |= DeleteDeadPHIs(L->getHeader());
// Check a post-condition.
@@ -1984,8 +1727,7 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
// Verify that LFTR, and any other change have not interfered with SCEV's
// ability to compute trip count.
#ifndef NDEBUG
- if (!EnableIVRewrite && VerifyIndvars &&
- !isa<SCEVCouldNotCompute>(BackedgeTakenCount)) {
+ if (VerifyIndvars && !isa<SCEVCouldNotCompute>(BackedgeTakenCount)) {
SE->forgetLoop(L);
const SCEV *NewBECount = SE->getBackedgeTakenCount(L);
if (SE->getTypeSizeInBits(BackedgeTakenCount->getType()) <
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