Factor some code into a new FoldSingleEntryPHINodes method.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60501 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index 45cfe8f..431424e 100644
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -54,6 +54,24 @@
BB->eraseFromParent();
}
+/// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are
+/// any single-entry PHI nodes in it, fold them away. This handles the case
+/// when all entries to the PHI nodes in a block are guaranteed equal, such as
+/// when the block has exactly one predecessor.
+void llvm::FoldSingleEntryPHINodes(BasicBlock *BB) {
+ if (!isa<PHINode>(BB->begin()))
+ return;
+
+ while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
+ if (PN->getIncomingValue(0) != PN)
+ PN->replaceAllUsesWith(PN->getIncomingValue(0));
+ else
+ PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+ PN->eraseFromParent();
+ }
+}
+
+
/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
/// if possible. The return value indicates success or failure.
bool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) {
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index f4faeb3..d6465f5 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1101,10 +1101,7 @@
// Degenerate case of a single entry PHI.
if (PN->getNumIncomingValues() == 1) {
- if (PN->getIncomingValue(0) != PN)
- PN->replaceAllUsesWith(PN->getIncomingValue(0));
- else
- PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+ FoldSingleEntryPHINodes(PN->getParent());
PN->eraseFromParent();
return true;
}
diff --git a/lib/Transforms/Utils/UnrollLoop.cpp b/lib/Transforms/Utils/UnrollLoop.cpp
index 63493dc..caef7ec 100644
--- a/lib/Transforms/Utils/UnrollLoop.cpp
+++ b/lib/Transforms/Utils/UnrollLoop.cpp
@@ -25,13 +25,14 @@
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include <cstdio>
using namespace llvm;
-/* TODO: Should these be here or in LoopUnroll? */
+// TODO: Should these be here or in LoopUnroll?
STATISTIC(NumCompletelyUnrolled, "Number of loops completely unrolled");
STATISTIC(NumUnrolled, "Number of loops unrolled (completely or otherwise)");
@@ -68,11 +69,7 @@
// multiple duplicate (but guaranteed to be equal) entries for the
// incoming edges. This occurs when there are multiple edges from
// OnlyPred to OnlySucc.
- //
- while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
- PN->replaceAllUsesWith(PN->getIncomingValue(0));
- BB->getInstList().pop_front(); // Delete the phi node...
- }
+ FoldSingleEntryPHINodes(BB);
// Delete the unconditional branch from the predecessor...
OnlyPred->getInstList().pop_back();