Make LoopDeletion work on loops with multiple edges, as long as the incoming
values from all of the loop's exiting blocks are equal. Patch by Andrew Clinton.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126253 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopDeletion.cpp b/lib/Transforms/Scalar/LoopDeletion.cpp
index 6d1d344..753a558 100644
--- a/lib/Transforms/Scalar/LoopDeletion.cpp
+++ b/lib/Transforms/Scalar/LoopDeletion.cpp
@@ -78,7 +78,6 @@
SmallVector<BasicBlock*, 4>& exitingBlocks,
SmallVector<BasicBlock*, 4>& exitBlocks,
bool &Changed, BasicBlock *Preheader) {
- BasicBlock* exitingBlock = exitingBlocks[0];
BasicBlock* exitBlock = exitBlocks[0];
// Make sure that all PHI entries coming from the loop are loop invariant.
@@ -88,11 +87,21 @@
// of the loop.
BasicBlock::iterator BI = exitBlock->begin();
while (PHINode* P = dyn_cast<PHINode>(BI)) {
- Value* incoming = P->getIncomingValueForBlock(exitingBlock);
+ Value* incoming = P->getIncomingValueForBlock(exitingBlocks[0]);
+
+ // Make sure all exiting blocks produce the same incoming value for the exit
+ // block. If there are different incoming values for different exiting
+ // blocks, then it is impossible to statically determine which value should
+ // be used.
+ for (unsigned i = 1; i < exitingBlocks.size(); ++i) {
+ if (incoming != P->getIncomingValueForBlock(exitingBlocks[i]))
+ return false;
+ }
+
if (Instruction* I = dyn_cast<Instruction>(incoming))
if (!L->makeLoopInvariant(I, Changed, Preheader->getTerminator()))
return false;
-
+
++BI;
}
@@ -147,10 +156,6 @@
if (exitBlocks.size() != 1)
return false;
- // Loops with multiple exits are too complicated to handle correctly.
- if (exitingBlocks.size() != 1)
- return false;
-
// Finally, we have to check that the loop really is dead.
bool Changed = false;
if (!IsLoopDead(L, exitingBlocks, exitBlocks, Changed, preheader))
@@ -166,7 +171,6 @@
// Now that we know the removal is safe, remove the loop by changing the
// branch from the preheader to go to the single exit block.
BasicBlock* exitBlock = exitBlocks[0];
- BasicBlock* exitingBlock = exitingBlocks[0];
// Because we're deleting a large chunk of code at once, the sequence in which
// we remove things is very important to avoid invalidation issues. Don't
@@ -183,9 +187,12 @@
// Rewrite phis in the exit block to get their inputs from
// the preheader instead of the exiting block.
+ BasicBlock* exitingBlock = exitingBlocks[0];
BasicBlock::iterator BI = exitBlock->begin();
while (PHINode* P = dyn_cast<PHINode>(BI)) {
P->replaceUsesOfWith(exitingBlock, preheader);
+ for (unsigned i = 1; i < exitingBlocks.size(); ++i)
+ P->removeIncomingValue(exitingBlocks[i]);
++BI;
}