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
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 @@
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 @@
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 @@
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 @@
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();