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/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index 6ee1fd6..4fe08e4 100644
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -384,17 +384,18 @@
// in this loop, insert a canonical induction variable of the largest size.
Value *IndVar = 0;
if (NeedCannIV) {
- // Check to see if the loop already has a canonical-looking induction
- // variable. If one is present and it's wider than the planned canonical
- // induction variable, temporarily remove it, so that the Rewriter
- // doesn't attempt to reuse it.
- PHINode *OldCannIV = L->getCanonicalInductionVariable();
- if (OldCannIV) {
+ // 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
- OldCannIV = 0;
+ break;
+ OldCannIVs.push_back(OldCannIV);
}
IndVar = Rewriter.getOrInsertCanonicalInductionVariable(L, LargestType);
@@ -404,17 +405,21 @@
DEBUG(dbgs() << "INDVARS: New CanIV: " << *IndVar << '\n');
// Now that the official induction variable is established, reinsert
- // the old canonical-looking variable after it so that the IR remains
- // consistent. It will be deleted as part of the dead-PHI deletion at
+ // 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.
- if (OldCannIV)
- OldCannIV->insertAfter(cast<Instruction>(IndVar));
+ while (!OldCannIVs.empty()) {
+ PHINode *OldCannIV = OldCannIVs.pop_back_val();
+ OldCannIV->insertBefore(L->getHeader()->getFirstNonPHI());
+ }
}
// If we have a trip count expression, rewrite the loop's exit condition
// using it. We can currently only handle loops with a single exit.
ICmpInst *NewICmp = 0;
- if (!isa<SCEVCouldNotCompute>(BackedgeTakenCount) && ExitingBlock) {
+ if (!isa<SCEVCouldNotCompute>(BackedgeTakenCount) &&
+ !BackedgeTakenCount->isZero() &&
+ ExitingBlock) {
assert(NeedCannIV &&
"LinearFunctionTestReplace requires a canonical induction variable");
// Can't rewrite non-branch yet.