[asan] make sure that the crash callbacks do not get merged (Chandler's idea: insert an empty InlineAsm). Change the order in which the new BBs are inserted: the slow path BB is insert between old BBs, the crash BB is inserted at the end. Don't create an empty BB (introduced by recent commits). Update the test. The experimental code that does manual crash callback merge will most likely be deleted later.

llvm-svn: 160544

1 files changed, 16 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index 14348b9bac6..336802668ca 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -18,6 +18,7 @@
 #include "FunctionBlackList.h"
 #include "llvm/Function.h"
 #include "llvm/IRBuilder.h"
+#include "llvm/InlineAsm.h"
 #include "llvm/IntrinsicInst.h"
 #include "llvm/LLVMContext.h"
 #include "llvm/Module.h"
@@ -224,6 +225,7 @@ struct AddressSanitizer : public ModulePass {
   OwningPtr<FunctionBlackList> BL;
   // This array is indexed by AccessIsWrite and log2(AccessSize).
   Function *AsanErrorCallback[2][kNumberOfAccessSizes];
+  InlineAsm *EmptyAsm;
 };
 
 }  // namespace
@@ -276,7 +278,7 @@ static BranchInst *splitBlockAndInsertIfThen(Value *Cmp,
   BranchInst *CheckTerm = 0;
   if (!ThenBlock) {
     LLVMContext &C = Head->getParent()->getParent()->getContext();
-    ThenBlock = BasicBlock::Create(C, "", Head->getParent());
+    ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
     CheckTerm = BranchInst::Create(Tail, ThenBlock);
   }
   BranchInst *HeadNewTerm =
@@ -414,7 +416,10 @@ Instruction *AddressSanitizer::generateCrashCode(
                            Addr, PC);
   else
     Call = IRB.CreateCall(AsanErrorCallback[IsWrite][AccessSizeIndex], Addr);
-  Call->setDoesNotReturn();
+  // We don't do Call->setDoesNotReturn() because the BB already has
+  // UnreachableInst at the end.
+  // This EmptyAsm is required to avoid callback merge.
+  IRB.CreateCall(EmptyAsm);
   return Call;
 }
 
@@ -483,10 +488,13 @@ void AddressSanitizer::instrumentAddress(AsanFunctionContext &AFC,
 
   size_t Granularity = 1 << MappingScale;
   if (TypeSize < 8 * Granularity) {
-    Instruction *CheckTerm = splitBlockAndInsertIfThen(Cmp);
+    BranchInst *CheckTerm = splitBlockAndInsertIfThen(Cmp);
+    assert(CheckTerm->isUnconditional());
+    BasicBlock *NextBB = CheckTerm->getSuccessor(0);
     IRB.SetInsertPoint(CheckTerm);
     Value *Cmp2 = createSlowPathCmp(IRB, AddrLong, ShadowValue, TypeSize);
-    splitBlockAndInsertIfThen(Cmp2, CrashBlock);
+    BranchInst *NewTerm = BranchInst::Create(CrashBlock, NextBB, Cmp2);
+    ReplaceInstWithInst(CheckTerm, NewTerm);
   } else {
     splitBlockAndInsertIfThen(Cmp, CrashBlock);
   }
@@ -695,6 +703,10 @@ bool AddressSanitizer::runOnModule(Module &M) {
           M.getOrInsertFunction(FunctionName, IRB.getVoidTy(), IntptrTy, NULL));
     }
   }
+  // We insert an empty inline asm after __asan_report* to avoid callback merge.
+  EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
+                            StringRef(""), StringRef(""),
+                            /*hasSideEffects=*/true);
 
   llvm::Triple targetTriple(M.getTargetTriple());
   bool isAndroid = targetTriple.getEnvironment() == llvm::Triple::ANDROIDEABI;