From 01fcec965e45a246e8f00596467dae3d48eab695 Mon Sep 17 00:00:00 2001
From: Peizhao Ou <peizhaoo@uci.edu>
Date: Wed, 29 Nov 2017 10:14:44 -0800
Subject: [PATCH] Fixes a bug in finding the upcoming store/conditional branch
 instruction

---
 lib/CodeGen/CodeGenPrepare.cpp | 38 ++++++++++++++--------------------
 lib/IR/Verifier.cpp            |  3 +++
 2 files changed, 18 insertions(+), 23 deletions(-)

diff --git a/lib/CodeGen/CodeGenPrepare.cpp b/lib/CodeGen/CodeGenPrepare.cpp
index 5c9858dcec2..d7037a93200 100644
--- a/lib/CodeGen/CodeGenPrepare.cpp
+++ b/lib/CodeGen/CodeGenPrepare.cpp
@@ -667,32 +667,23 @@ Instruction* findFirstStoreCondBranchInst(LoadInst* LI) {
   auto BE = BB->end();
   auto BBI = BasicBlock::iterator(LI);
   BBI++;
-  while (true) {
-    for (; BBI != BE; BBI++) {
-      auto* Inst = dyn_cast<Instruction>(&*BBI);
-      if (Inst == nullptr) {
-        continue;
-      }
-      if (Inst->getOpcode() == Instruction::Store) {
+  for (; BBI != BE; BBI++) {
+    auto* Inst = dyn_cast<Instruction>(&*BBI);
+    if (Inst == nullptr) {
+      continue;
+    }
+    if (Inst->getOpcode() == Instruction::Store) {
+      return Inst;
+    } else if (Inst->getOpcode() == Instruction::Br) {
+      auto* BrInst = dyn_cast<BranchInst>(Inst);
+      if (BrInst->isConditional()) {
         return Inst;
-      } else if (Inst->getOpcode() == Instruction::Br) {
-        auto* BrInst = dyn_cast<BranchInst>(Inst);
-        if (BrInst->isConditional()) {
-          return Inst;
-        } else {
-          // Reinitialize iterators with the destination of the unconditional
-          // branch.
-          BB = BrInst->getSuccessor(0);
-          BBI = BB->begin();
-          BE = BB->end();
-          break;
-        }
+      } else {
+        return nullptr;
       }
     }
-    if (BBI == BE) {
-      return nullptr;
-    }
   }
+  return nullptr;
 }
 
 // XXX-comment: Returns whether the code has been changed.
@@ -780,7 +771,8 @@ bool AddFakeConditionalBranchAfterMonotonicLoads(
         if (StoreAddressDependOnValue(dyn_cast<StoreInst>(FirstInst), LI)) {
           continue;
         }
-      } else if (FirstInst->getOpcode() == Instruction::Br) {
+      } else if (FirstInst->getOpcode() == Instruction::Br &&
+                 isa<BranchInst>(FirstInst)) {
         if (ConditionalBranchDependsOnValue(dyn_cast<BranchInst>(FirstInst),
                                             LI)) {
           continue;
diff --git a/lib/IR/Verifier.cpp b/lib/IR/Verifier.cpp
index 9198b0e1fb5..ba6bbb1f637 100644
--- a/lib/IR/Verifier.cpp
+++ b/lib/IR/Verifier.cpp
@@ -3354,6 +3354,9 @@ void Verifier::verifyDominatesUse(Instruction &I, unsigned i) {
   }
 
   const Use &U = I.getOperandUse(i);
+  if (!(InstsInThisBlock.count(Op) || DT.dominates(Op, U))) {
+    i = *((unsigned*) nullptr);
+  }
   Assert(InstsInThisBlock.count(Op) || DT.dominates(Op, U),
          "Instruction does not dominate all uses!", Op, &I);
 }
-- 
2.34.1