From 6de2c08bc400b4aca9fb46684e8bdb56eed9b09f Mon Sep 17 00:00:00 2001
From: dim <dim@FreeBSD.org>
Date: Sun, 2 Dec 2012 13:10:19 +0000
Subject: Vendor import of llvm release_32 branch r168974 (effectively, 3.2
 RC2): http://llvm.org/svn/llvm-project/llvm/branches/release_32@168974

---
 lib/Transforms/Utils/PromoteMemoryToRegister.cpp | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

(limited to 'lib/Transforms/Utils/PromoteMemoryToRegister.cpp')

diff --git a/lib/Transforms/Utils/PromoteMemoryToRegister.cpp b/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
index dd5e20e..558de9d 100644
--- a/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
+++ b/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
@@ -212,9 +212,13 @@ namespace {
     ///
     DenseMap<AllocaInst*, unsigned>  AllocaLookup;
 
-    /// NewPhiNodes - The PhiNodes we're adding.
+    /// NewPhiNodes - The PhiNodes we're adding.  That map is used to simplify
+    /// some Phi nodes as we iterate over it, so it should have deterministic
+    /// iterators.  We could use a MapVector, but since we already maintain a
+    /// map from BasicBlock* to a stable numbering (BBNumbers), the DenseMap is
+    /// more efficient (also supports removal).
     ///
-    DenseMap<std::pair<BasicBlock*, unsigned>, PHINode*> NewPhiNodes;
+    DenseMap<std::pair<unsigned, unsigned>, PHINode*> NewPhiNodes;
     
     /// PhiToAllocaMap - For each PHI node, keep track of which entry in Allocas
     /// it corresponds to.
@@ -588,7 +592,11 @@ void PromoteMem2Reg::run() {
   while (EliminatedAPHI) {
     EliminatedAPHI = false;
     
-    for (DenseMap<std::pair<BasicBlock*, unsigned>, PHINode*>::iterator I =
+    // Iterating over NewPhiNodes is deterministic, so it is safe to try to
+    // simplify and RAUW them as we go.  If it was not, we could add uses to
+    // the values we replace with in a non deterministic order, thus creating
+    // non deterministic def->use chains.
+    for (DenseMap<std::pair<unsigned, unsigned>, PHINode*>::iterator I =
            NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E;) {
       PHINode *PN = I->second;
 
@@ -612,7 +620,7 @@ void PromoteMem2Reg::run() {
   // have incoming values for all predecessors.  Loop over all PHI nodes we have
   // created, inserting undef values if they are missing any incoming values.
   //
-  for (DenseMap<std::pair<BasicBlock*, unsigned>, PHINode*>::iterator I =
+  for (DenseMap<std::pair<unsigned, unsigned>, PHINode*>::iterator I =
          NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E; ++I) {
     // We want to do this once per basic block.  As such, only process a block
     // when we find the PHI that is the first entry in the block.
@@ -992,7 +1000,7 @@ void PromoteMem2Reg::PromoteSingleBlockAlloca(AllocaInst *AI, AllocaInfo &Info,
 bool PromoteMem2Reg::QueuePhiNode(BasicBlock *BB, unsigned AllocaNo,
                                   unsigned &Version) {
   // Look up the basic-block in question.
-  PHINode *&PN = NewPhiNodes[std::make_pair(BB, AllocaNo)];
+  PHINode *&PN = NewPhiNodes[std::make_pair(BBNumbers[BB], AllocaNo)];
 
   // If the BB already has a phi node added for the i'th alloca then we're done!
   if (PN) return false;
-- 
cgit v1.1