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| author | Dan Gohman <gohman@apple.com> | 2009-05-18 15:36:09 +0000 |
|---|---|---|
| committer | Dan Gohman <gohman@apple.com> | 2009-05-18 15:36:09 +0000 |
| commit | ab157b247e2e3089c4c3727cc2993c14bf8ab6ed (patch) | |
| tree | ff62a31ebe98ed44b0e664bbbc8489b486f40fba /lib/Analysis/ScalarEvolution.cpp | |
| parent | f8bc8e8ad3c5c50822ff96ce811629ff35026e3f (diff) | |
| download | external_llvm-ab157b247e2e3089c4c3727cc2993c14bf8ab6ed.zip external_llvm-ab157b247e2e3089c4c3727cc2993c14bf8ab6ed.tar.gz external_llvm-ab157b247e2e3089c4c3727cc2993c14bf8ab6ed.tar.bz2 | |
Make ScalarEvolution::isLoopGuardedByCond work even when the edge
entering a loop is a non-split critical edge.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72004 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Analysis/ScalarEvolution.cpp')
| -rw-r--r-- | lib/Analysis/ScalarEvolution.cpp | 40 |
1 files changed, 27 insertions, 13 deletions
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index 4b99a86..f300039 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -3246,6 +3246,21 @@ SCEVHandle ScalarEvolution::HowFarToNonZero(const SCEV *V, const Loop *L) { return UnknownValue; } +/// getLoopPredecessor - If the given loop's header has exactly one unique +/// predecessor outside the loop, return it. Otherwise return null. +/// +BasicBlock *ScalarEvolution::getLoopPredecessor(const Loop *L) { + BasicBlock *Header = L->getHeader(); + BasicBlock *Pred = 0; + for (pred_iterator PI = pred_begin(Header), E = pred_end(Header); + PI != E; ++PI) + if (!L->contains(*PI)) { + if (Pred && Pred != *PI) return 0; // Multiple predecessors. + Pred = *PI; + } + return Pred; +} + /// getPredecessorWithUniqueSuccessorForBB - Return a predecessor of BB /// (which may not be an immediate predecessor) which has exactly one /// successor from which BB is reachable, or null if no such block is @@ -3260,11 +3275,10 @@ ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) { return Pred; // A loop's header is defined to be a block that dominates the loop. - // If the loop has a preheader, it must be a block that has exactly - // one successor that can reach BB. This is slightly more strict - // than necessary, but works if critical edges are split. + // If the header has a unique predecessor outside the loop, it must be + // a block that has exactly one successor that can reach the loop. if (Loop *L = LI->getLoopFor(BB)) - return L->getLoopPreheader(); + return getLoopPredecessor(L); return 0; } @@ -3275,18 +3289,18 @@ ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) { bool ScalarEvolution::isLoopGuardedByCond(const Loop *L, ICmpInst::Predicate Pred, const SCEV *LHS, const SCEV *RHS) { - BasicBlock *Preheader = L->getLoopPreheader(); - BasicBlock *PreheaderDest = L->getHeader(); + BasicBlock *Predecessor = getLoopPredecessor(L); + BasicBlock *PredecessorDest = L->getHeader(); - // Starting at the preheader, climb up the predecessor chain, as long as - // there are predecessors that can be found that have unique successors + // Starting at the loop predecessor, climb up the predecessor chain, as long + // as there are predecessors that can be found that have unique successors // leading to the original header. - for (; Preheader; - PreheaderDest = Preheader, - Preheader = getPredecessorWithUniqueSuccessorForBB(Preheader)) { + for (; Predecessor; + PredecessorDest = Predecessor, + Predecessor = getPredecessorWithUniqueSuccessorForBB(Predecessor)) { BranchInst *LoopEntryPredicate = - dyn_cast<BranchInst>(Preheader->getTerminator()); + dyn_cast<BranchInst>(Predecessor->getTerminator()); if (!LoopEntryPredicate || LoopEntryPredicate->isUnconditional()) continue; @@ -3299,7 +3313,7 @@ bool ScalarEvolution::isLoopGuardedByCond(const Loop *L, Value *PreCondLHS = ICI->getOperand(0); Value *PreCondRHS = ICI->getOperand(1); ICmpInst::Predicate Cond; - if (LoopEntryPredicate->getSuccessor(0) == PreheaderDest) + if (LoopEntryPredicate->getSuccessor(0) == PredecessorDest) Cond = ICI->getPredicate(); else Cond = ICI->getInversePredicate(); |