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Make getPredecessorWithUniqueSuccessorForBB return the unique successor

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in addition to the predecessor.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101374 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2010-04-15 16:19:08 +00:00
parent 3181c50534
commit 005752bbe7
2 changed files with 12 additions and 13 deletions
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3
include/llvm/Analysis/ScalarEvolution.h
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@@ -351,7 +351,8 @@ namespace llvm {
/// (which may not be an immediate predecessor) which has exactly one /// (which may not be an immediate predecessor) which has exactly one
/// successor from which BB is reachable, or null if no such block is /// successor from which BB is reachable, or null if no such block is
/// found. /// found.
BasicBlock* getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB); std::pair<BasicBlock *, BasicBlock *>
getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB);
/// isImpliedCond - Test whether the condition described by Pred, LHS, /// isImpliedCond - Test whether the condition described by Pred, LHS,
/// and RHS is true whenever the given Cond value evaluates to true. /// and RHS is true whenever the given Cond value evaluates to true.

22
lib/Analysis/ScalarEvolution.cpp
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@@ -4654,21 +4654,21 @@ BasicBlock *ScalarEvolution::getLoopPredecessor(const Loop *L) {
/// successor from which BB is reachable, or null if no such block is /// successor from which BB is reachable, or null if no such block is
/// found. /// found.
/// ///
BasicBlock * std::pair<BasicBlock *, BasicBlock *>
ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) { ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
// If the block has a unique predecessor, then there is no path from the // If the block has a unique predecessor, then there is no path from the
// predecessor to the block that does not go through the direct edge // predecessor to the block that does not go through the direct edge
// from the predecessor to the block. // from the predecessor to the block.
if (BasicBlock *Pred = BB->getSinglePredecessor()) if (BasicBlock *Pred = BB->getSinglePredecessor())
return Pred; return std::make_pair(Pred, BB);
// A loop's header is defined to be a block that dominates the loop. // A loop's header is defined to be a block that dominates the loop.
// If the header has a unique predecessor outside the loop, it must be // 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. // a block that has exactly one successor that can reach the loop.
if (Loop *L = LI->getLoopFor(BB)) if (Loop *L = LI->getLoopFor(BB))
return getLoopPredecessor(L); return std::make_pair(getLoopPredecessor(L), L->getHeader());
return 0; return std::pair<BasicBlock *, BasicBlock *>();
} }
/// HasSameValue - SCEV structural equivalence is usually sufficient for /// HasSameValue - SCEV structural equivalence is usually sufficient for
@@ -4852,24 +4852,22 @@ ScalarEvolution::isLoopEntryGuardedByCond(const Loop *L,
// (interprocedural conditions notwithstanding). // (interprocedural conditions notwithstanding).
if (!L) return false; if (!L) return false;
BasicBlock *Predecessor = getLoopPredecessor(L);
BasicBlock *PredecessorDest = L->getHeader();
// Starting at the loop predecessor, climb up the predecessor chain, as long // Starting at the loop predecessor, climb up the predecessor chain, as long
// as there are predecessors that can be found that have unique successors // as there are predecessors that can be found that have unique successors
// leading to the original header. // leading to the original header.
for (; Predecessor; for (std::pair<BasicBlock *, BasicBlock *>
PredecessorDest = Predecessor, Pair(getLoopPredecessor(L), L->getHeader());
Predecessor = getPredecessorWithUniqueSuccessorForBB(Predecessor)) { Pair.first;
Pair = getPredecessorWithUniqueSuccessorForBB(Pair.first)) {
BranchInst *LoopEntryPredicate = BranchInst *LoopEntryPredicate =
dyn_cast<BranchInst>(Predecessor->getTerminator()); dyn_cast<BranchInst>(Pair.first->getTerminator());
if (!LoopEntryPredicate || if (!LoopEntryPredicate ||
LoopEntryPredicate->isUnconditional()) LoopEntryPredicate->isUnconditional())
continue; continue;
if (isImpliedCond(LoopEntryPredicate->getCondition(), Pred, LHS, RHS, if (isImpliedCond(LoopEntryPredicate->getCondition(), Pred, LHS, RHS,
LoopEntryPredicate->getSuccessor(0) != PredecessorDest)) LoopEntryPredicate->getSuccessor(0) != Pair.second))
return true; return true;
} }