From 91b65c0b42b3d5dece246bdb366441d6f5593396 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Mon, 29 Jul 2002 21:26:30 +0000
Subject: Allow folding of basic blocks that have PHI nodes in them, fixing
"bug": test/Regression/Transforms/SimplifyCFG/2002-06-24-PHINode.ll
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3128 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/Transforms/Utils/SimplifyCFG.cpp | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
(limited to 'lib/Transforms')
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 426d18e..59ea986 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -143,7 +143,7 @@ bool SimplifyCFG(BasicBlock *BB) {
// pred, and if there is only one distinct successor of the predecessor, and
// if there are no PHI nodes.
//
- if (!isa<PHINode>(BB->front()) && !BB->hasConstantReferences()) {
+ if (!BB->hasConstantReferences()) {
pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
BasicBlock *OnlyPred = *PI++;
for (; PI != PE; ++PI) // Search all predecessors, see if they are all same
@@ -168,6 +168,16 @@ bool SimplifyCFG(BasicBlock *BB) {
//cerr << "Merging: " << BB << "into: " << OnlyPred;
TerminatorInst *Term = OnlyPred->getTerminator();
+ // Resolve any PHI nodes at the start of the block. They are all
+ // guaranteed to have exactly one entry if they exist.
+ //
+ while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
+ assert(PN->getNumIncomingValues() == 1 && "Only one pred!");
+ PN->replaceAllUsesWith(PN->getIncomingValue(0));
+ BB->getInstList().pop_front(); // Delete the phi node...
+ }
+
+
// Delete the unconditional branch from the predecessor...
OnlyPred->getInstList().pop_back();
--
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