Make LoopSimplify change conditional branches in loop exiting blocks
which branch on undef to branch on a boolean constant for the edge
exiting the loop. This helps ScalarEvolution compute trip counts for
loops.
Teach ScalarEvolution to recognize single-value PHIs, when safe, and
ForgetSymbolicName to forget such single-value PHI nodes as apprpriate
in ForgetSymbolicName.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97126 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/LoopSimplify.cpp b/lib/Transforms/Utils/LoopSimplify.cpp
index 57bab60..2e1f935 100644
--- a/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/lib/Transforms/Utils/LoopSimplify.cpp
@@ -159,6 +159,22 @@
}
}
+ // If there are exiting blocks with branches on undef, resolve the undef in
+ // the direction which will exit the loop. This will help simplify loop
+ // trip count computations.
+ SmallVector<BasicBlock*, 8> ExitingBlocks;
+ L->getExitingBlocks(ExitingBlocks);
+ for (SmallVectorImpl<BasicBlock *>::iterator I = ExitingBlocks.begin(),
+ E = ExitingBlocks.end(); I != E; ++I)
+ if (BranchInst *BI = dyn_cast<BranchInst>((*I)->getTerminator()))
+ if (BI->isConditional()) {
+ if (UndefValue *Cond = dyn_cast<UndefValue>(BI->getCondition())) {
+ BI->setCondition(ConstantInt::get(Cond->getType(),
+ !L->contains(BI->getSuccessor(0))));
+ Changed = true;
+ }
+ }
+
// Does the loop already have a preheader? If so, don't insert one.
BasicBlock *Preheader = L->getLoopPreheader();
if (!Preheader) {
@@ -250,8 +266,6 @@
break;
}
if (UniqueExit) {
- SmallVector<BasicBlock*, 8> ExitingBlocks;
- L->getExitingBlocks(ExitingBlocks);
for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
BasicBlock *ExitingBlock = ExitingBlocks[i];
if (!ExitingBlock->getSinglePredecessor()) continue;