From ebd6454929f2ba3b92f61c151eccde0b8b0a8ded Mon Sep 17 00:00:00 2001
From: Kostya Serebryany <kcc@google.com>
Date: Tue, 14 Aug 2012 14:04:51 +0000
Subject: [PATCH] [asan] insert crash basic blocks inline as opposed to
 inserting them at the end of the function. This doesn't seem to fix or break
 anything, but is considered to be more friendly to downstream passes

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161870 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Instrumentation/AddressSanitizer.cpp      | 57 +++++++++----------
 1 file changed, 27 insertions(+), 30 deletions(-)

diff --git a/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index bf35eacd69f..3d5424951c1 100644
--- a/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -159,7 +159,7 @@ struct AddressSanitizer : public ModulePass {
                          Value *Addr, uint32_t TypeSize, bool IsWrite);
   Value *createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
                            Value *ShadowValue, uint32_t TypeSize);
-  Instruction *generateCrashCode(BasicBlock *BB, Value *Addr, Value *PC,
+  Instruction *generateCrashCode(Instruction *InsertBefore, Value *Addr,
                                  bool IsWrite, size_t AccessSizeIndex);
   bool instrumentMemIntrinsic(AsanFunctionContext &AFC, MemIntrinsic *MI);
   void instrumentMemIntrinsicParam(AsanFunctionContext &AFC,
@@ -251,24 +251,24 @@ static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str) {
 //     ThenBlock
 //   Tail
 //
-// If ThenBlock is zero, a new block is created and its terminator is returned.
-// Otherwize 0 is returned.
-static BranchInst *splitBlockAndInsertIfThen(Value *Cmp,
-                                             BasicBlock *ThenBlock = 0) {
+// ThenBlock block is created and its terminator is returned.
+// If Unreachable, ThenBlock is terminated with UnreachableInst, otherwise
+// it is terminated with BranchInst to Tail.
+static TerminatorInst *splitBlockAndInsertIfThen(Value *Cmp, bool Unreachable) {
   Instruction *SplitBefore = cast<Instruction>(Cmp)->getNextNode();
   BasicBlock *Head = SplitBefore->getParent();
   BasicBlock *Tail = Head->splitBasicBlock(SplitBefore);
   TerminatorInst *HeadOldTerm = Head->getTerminator();
-  BranchInst *CheckTerm = 0;
-  if (!ThenBlock) {
-    LLVMContext &C = Head->getParent()->getParent()->getContext();
-    ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
+  LLVMContext &C = Head->getParent()->getParent()->getContext();
+  BasicBlock *ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
+  TerminatorInst *CheckTerm;
+  if (Unreachable)
+    CheckTerm = new UnreachableInst(C, ThenBlock);
+  else
     CheckTerm = BranchInst::Create(Tail, ThenBlock);
-  }
   BranchInst *HeadNewTerm =
     BranchInst::Create(/*ifTrue*/ThenBlock, /*ifFalse*/Tail, Cmp);
   ReplaceInstWithInst(HeadOldTerm, HeadNewTerm);
-
   return CheckTerm;
 }
 
@@ -320,7 +320,7 @@ bool AddressSanitizer::instrumentMemIntrinsic(AsanFunctionContext &AFC,
 
     Value *Cmp = IRB.CreateICmpNE(Length,
                                   Constant::getNullValue(Length->getType()));
-    InsertBefore = splitBlockAndInsertIfThen(Cmp);
+    InsertBefore = splitBlockAndInsertIfThen(Cmp, false);
   }
 
   instrumentMemIntrinsicParam(AFC, MI, Dst, Length, InsertBefore, true);
@@ -391,15 +391,11 @@ Function *AddressSanitizer::checkInterfaceFunction(Constant *FuncOrBitcast) {
 }
 
 Instruction *AddressSanitizer::generateCrashCode(
-    BasicBlock *BB, Value *Addr, Value *PC,
+    Instruction *InsertBefore, Value *Addr,
     bool IsWrite, size_t AccessSizeIndex) {
-  IRBuilder<> IRB(BB->getFirstNonPHI());
-  CallInst *Call;
-  if (PC)
-    Call = IRB.CreateCall2(AsanErrorCallback[IsWrite][AccessSizeIndex],
-                           Addr, PC);
-  else
-    Call = IRB.CreateCall(AsanErrorCallback[IsWrite][AccessSizeIndex], Addr);
+  IRBuilder<> IRB(InsertBefore);
+  CallInst *Call = IRB.CreateCall(AsanErrorCallback[IsWrite][AccessSizeIndex],
+                                  Addr);
   // We don't do Call->setDoesNotReturn() because the BB already has
   // UnreachableInst at the end.
   // This EmptyAsm is required to avoid callback merge.
@@ -440,26 +436,27 @@ void AddressSanitizer::instrumentAddress(AsanFunctionContext &AFC,
       IRB.CreateIntToPtr(ShadowPtr, ShadowPtrTy));
 
   Value *Cmp = IRB.CreateICmpNE(ShadowValue, CmpVal);
-
-  BasicBlock *CrashBlock = BasicBlock::Create(*C, "crash_bb", &AFC.F);
-  new UnreachableInst(*C, CrashBlock);
   size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize);
-  Instruction *Crash =
-      generateCrashCode(CrashBlock, AddrLong, 0, IsWrite, AccessSizeIndex);
-  Crash->setDebugLoc(OrigIns->getDebugLoc());
-
   size_t Granularity = 1 << MappingScale;
+  TerminatorInst *CrashTerm = 0;
+
   if (TypeSize < 8 * Granularity) {
-    BranchInst *CheckTerm = splitBlockAndInsertIfThen(Cmp);
-    assert(CheckTerm->isUnconditional());
+    TerminatorInst *CheckTerm = splitBlockAndInsertIfThen(Cmp, false);
+    assert(dyn_cast<BranchInst>(CheckTerm)->isUnconditional());
     BasicBlock *NextBB = CheckTerm->getSuccessor(0);
     IRB.SetInsertPoint(CheckTerm);
     Value *Cmp2 = createSlowPathCmp(IRB, AddrLong, ShadowValue, TypeSize);
+    BasicBlock *CrashBlock = BasicBlock::Create(*C, "", &AFC.F, NextBB);
+    CrashTerm = new UnreachableInst(*C, CrashBlock);
     BranchInst *NewTerm = BranchInst::Create(CrashBlock, NextBB, Cmp2);
     ReplaceInstWithInst(CheckTerm, NewTerm);
   } else {
-    splitBlockAndInsertIfThen(Cmp, CrashBlock);
+    CrashTerm = splitBlockAndInsertIfThen(Cmp, true);
   }
+
+  Instruction *Crash =
+      generateCrashCode(CrashTerm, AddrLong, IsWrite, AccessSizeIndex);
+  Crash->setDebugLoc(OrigIns->getDebugLoc());
 }
 
 // This function replaces all global variables with new variables that have
-- 
2.34.1