[simplifycfg][loop-simplify] Preserve loop metadata in 2 transformations.
insertUniqueBackedgeBlock in lib/Transforms/Utils/LoopSimplify.cpp now
propagates existing llvm.loop metadata to newly the added backedge.
llvm::TryToSimplifyUncondBranchFromEmptyBlock in lib/Transforms/Utils/Local.cpp
now propagates existing llvm.loop metadata to the branch instructions in the
predecessor blocks of the empty block that is removed.
Differential Revision: https://reviews.llvm.org/D26495
llvm-svn: 287341
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 0483c1e..3ad5f58 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -890,6 +890,17 @@
}
}
+ // If the unconditional branch we replaced contains llvm.loop metadata, we
+ // add the metadata to the branch instructions in the predecessors.
+ unsigned LoopMDKind = BB->getContext().getMDKindID("llvm.loop");
+ Instruction *TI = BB->getTerminator();
+ if (TI)
+ if (MDNode *LoopMD = TI->getMetadata(LoopMDKind))
+ for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
+ BasicBlock *Pred = *PI;
+ Pred->getTerminator()->setMetadata(LoopMDKind, LoopMD);
+ }
+
// Everything that jumped to BB now goes to Succ.
BB->replaceAllUsesWith(Succ);
if (!Succ->hasName()) Succ->takeName(BB);
diff --git a/llvm/lib/Transforms/Utils/LoopSimplify.cpp b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
index 89933e0..d24c1c4 100644
--- a/llvm/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
@@ -470,13 +470,21 @@
}
// Now that all of the PHI nodes have been inserted and adjusted, modify the
- // backedge blocks to just to the BEBlock instead of the header.
+ // backedge blocks to jump to the BEBlock instead of the header.
+ // If one of the backedges has llvm.loop metadata attached, we remove
+ // it from the backedge and add it to BEBlock.
+ unsigned LoopMDKind = BEBlock->getContext().getMDKindID("llvm.loop");
+ MDNode *LoopMD = nullptr;
for (unsigned i = 0, e = BackedgeBlocks.size(); i != e; ++i) {
TerminatorInst *TI = BackedgeBlocks[i]->getTerminator();
+ if (!LoopMD)
+ LoopMD = TI->getMetadata(LoopMDKind);
+ TI->setMetadata(LoopMDKind, nullptr);
for (unsigned Op = 0, e = TI->getNumSuccessors(); Op != e; ++Op)
if (TI->getSuccessor(Op) == Header)
TI->setSuccessor(Op, BEBlock);
}
+ BEBlock->getTerminator()->setMetadata(LoopMDKind, LoopMD);
//===--- Update all analyses which we must preserve now -----------------===//