2 files changed, 43 insertions, 18 deletions

diff --git a/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp b/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
index 28a31a97025..0fca617be7e 100644
--- a/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
@@ -148,6 +148,8 @@ void ConstantHoisting::CollectConstant(User * U, unsigned Opcode,
     ConstantCandidate &CC = ConstantMap[C];
     CC.CumulativeCost += Cost;
     CC.Uses.push_back(U);
+    DEBUG(dbgs() << "Collect constant " << *C << " with cost " << Cost
+                 << " from " << *U << '\n');
   }
 }
 
@@ -279,6 +281,20 @@ static void CollectBasicBlocks(SmallPtrSet<BasicBlock *, 4> &BBs, Function &F,
           BBs.insert(I->getParent());
 }
 
+/// \brief Find the instruction we should insert the constant materialization
+/// before.
+static Instruction *getMatInsertPt(Instruction *I, const DominatorTree *DT) {
+  if (!isa<PHINode>(I) && !isa<LandingPadInst>(I)) // Simple case.
+    return I;
+
+  // We can't insert directly before a phi node or landing pad. Insert before
+  // the terminator of the dominating block.
+  assert(&I->getParent()->getParent()->getEntryBlock() != I->getParent() &&
+         "PHI or landing pad in entry block!");
+  BasicBlock *IDom = DT->getNode(I->getParent())->getIDom()->getBlock();
+  return IDom->getTerminator();
+}
+
 /// \brief Find an insertion point that dominates all uses.
 Instruction *ConstantHoisting::
 FindConstantInsertionPoint(Function &F, const ConstantInfo &CI) const {
@@ -291,10 +307,10 @@ FindConstantInsertionPoint(Function &F, const ConstantInfo &CI) const {
        RCI != RCE; ++RCI)
     for (SmallVectorImpl<User *>::const_iterator U = RCI->Uses.begin(),
          E = RCI->Uses.end(); U != E; ++U)
-        CollectBasicBlocks(BBs, F, *U);
+      CollectBasicBlocks(BBs, F, *U);
 
   if (BBs.count(Entry))
-    return Entry->getFirstInsertionPt();
+    return getMatInsertPt(&Entry->front(), DT);
 
   while (BBs.size() >= 2) {
     BasicBlock *BB, *BB1, *BB2;
@@ -302,27 +318,14 @@ FindConstantInsertionPoint(Function &F, const ConstantInfo &CI) const {
     BB2 = *llvm::next(BBs.begin());
     BB = DT->findNearestCommonDominator(BB1, BB2);
     if (BB == Entry)
-      return Entry->getFirstInsertionPt();
+      return getMatInsertPt(&Entry->front(), DT);
     BBs.erase(BB1);
     BBs.erase(BB2);
     BBs.insert(BB);
   }
   assert((BBs.size() == 1) && "Expected only one element.");
-  return (*BBs.begin())->getFirstInsertionPt();
-}
-
-/// \brief Find the instruction we should insert the constant materialization
-/// before.
-static Instruction *getMatInsertPt(Instruction *I, const DominatorTree *DT) {
-  if (!isa<PHINode>(I) && !isa<LandingPadInst>(I)) // Simple case.
-    return I;
-
-  // We can't insert directly before a phi node or landing pad. Insert before
-  // the terminator of the dominating block.
-  assert(&I->getParent()->getParent()->getEntryBlock() != I->getParent() &&
-         "PHI or landing pad in entry block!");
-  BasicBlock *IDom = DT->getNode(I->getParent())->getIDom()->getBlock();
-  return IDom->getTerminator();
+  Instruction &FirstInst = (*BBs.begin())->front();
+  return getMatInsertPt(&FirstInst, DT);
 }
 
 /// \brief Emit materialization code for all rebased constants and update their
diff --git a/llvm/test/Transforms/ConstantHoisting/X86/phi.ll b/llvm/test/Transforms/ConstantHoisting/X86/phi.ll
index abbba81654a..cc2fdda40e7 100644
--- a/llvm/test/Transforms/ConstantHoisting/X86/phi.ll
+++ b/llvm/test/Transforms/ConstantHoisting/X86/phi.ll
@@ -46,3 +46,25 @@ return:
 }
 
 declare void @foo(i8*)
+
+; PR18768
+define i32 @test3(i1 %c) {
+entry:
+  br i1 %c, label %if.then, label %if.end3
+
+if.then:                                          ; preds = %entry
+  br label %if.end3
+
+if.end3:                                          ; preds = %if.then, %entry
+  %d.0 = phi i32* [ inttoptr (i64 985162435264511 to i32*), %entry ], [ null, %if.then ]
+  %cmp4 = icmp eq i32* %d.0, inttoptr (i64 985162435264511 to i32*)
+  %cmp6 = icmp eq i32* %d.0, inttoptr (i64 985162418487296 to i32*)
+  %or = or i1 %cmp4, %cmp6
+  br i1 %or, label %if.then8, label %if.end9
+
+if.then8:                                         ; preds = %if.end3
+  ret i32 1
+
+if.end9:                                          ; preds = %if.then8, %if.end3
+  ret i32 undef
+}