[IndVars] Factor out a helper function for readability [NFC]
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@375133 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index 2fb8d70..dc0a1da 100644
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -2646,31 +2646,44 @@
return MadeAnyChanges;
}
-bool IndVarSimplify::optimizeLoopExits(Loop *L, SCEVExpander &Rewriter) {
+/// Return a symbolic upper bound for the backedge taken count of the loop.
+/// This is more general than getConstantMaxBackedgeTakenCount as it returns
+/// an arbitrary expression as opposed to only constants.
+/// TODO: Move into the ScalarEvolution class.
+static const SCEV* getMaxBackedgeTakenCount(ScalarEvolution &SE,
+ DominatorTree &DT, Loop *L) {
SmallVector<BasicBlock*, 16> ExitingBlocks;
L->getExitingBlocks(ExitingBlocks);
// Form an expression for the maximum exit count possible for this loop. We
// merge the max and exact information to approximate a version of
// getConstantMaxBackedgeTakenCount which isn't restricted to just constants.
- // TODO: factor this out as a version of getConstantMaxBackedgeTakenCount which
- // isn't guaranteed to return a constant.
SmallVector<const SCEV*, 4> ExitCounts;
- const SCEV *MaxConstEC = SE->getConstantMaxBackedgeTakenCount(L);
+ const SCEV *MaxConstEC = SE.getConstantMaxBackedgeTakenCount(L);
if (!isa<SCEVCouldNotCompute>(MaxConstEC))
ExitCounts.push_back(MaxConstEC);
for (BasicBlock *ExitingBB : ExitingBlocks) {
- const SCEV *ExitCount = SE->getExitCount(L, ExitingBB);
+ const SCEV *ExitCount = SE.getExitCount(L, ExitingBB);
if (!isa<SCEVCouldNotCompute>(ExitCount)) {
- assert(DT->dominates(ExitingBB, L->getLoopLatch()) &&
+ assert(DT.dominates(ExitingBB, L->getLoopLatch()) &&
"We should only have known counts for exiting blocks that "
"dominate latch!");
ExitCounts.push_back(ExitCount);
}
}
if (ExitCounts.empty())
+ return SE.getCouldNotCompute();
+ return SE.getUMinFromMismatchedTypes(ExitCounts);
+}
+
+bool IndVarSimplify::optimizeLoopExits(Loop *L, SCEVExpander &Rewriter) {
+ SmallVector<BasicBlock*, 16> ExitingBlocks;
+ L->getExitingBlocks(ExitingBlocks);
+
+ // Get a symbolic upper bound on the loop backedge taken count.
+ const SCEV *MaxExitCount = getMaxBackedgeTakenCount(*SE, *DT, L);
+ if (isa<SCEVCouldNotCompute>(MaxExitCount))
return false;
- const SCEV *MaxExitCount = SE->getUMinFromMismatchedTypes(ExitCounts);
bool Changed = false;
for (BasicBlock *ExitingBB : ExitingBlocks) {
