commit c3c8db9d25e69083cec0c2d4a01735cd9e01269f
author Chandler Carruth <chandlerc@gmail.com> Mon Jul 16 08:58:53 2012 +0000
committer Chandler Carruth <chandlerc@gmail.com> Mon Jul 16 08:58:53 2012 +0000
tree 5f677cfa1b6471bb519bd1517ac8f78ece4a7184
parent 2f58533d1ec551878b770f8812474b836c32fd6e

Teach AddressSanitizer to create basic blocks in a more natural order.
This is particularly useful to the backend code generators which try to
process things in the incoming function order.

Also, cleanup some uses of IRBuilder to be a bit simpler and more clear.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160254 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Instrumentation/AddressSanitizer.cpp

diff --git a/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index 482ebef..45bcdf8 100644
--- a/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -230,17 +230,17 @@
 // Returns the ThenBlock's terminator.
 static BranchInst *splitBlockAndInsertIfThen(Value *Cmp) {
   Instruction *SplitBefore = cast<Instruction>(Cmp)->getNextNode();
-  BasicBlock *Head = SplitBefore->getParent();
-  BasicBlock *Tail = Head->splitBasicBlock(SplitBefore);
-  TerminatorInst *HeadOldTerm = Head->getTerminator();
-  LLVMContext &C = Head->getParent()->getParent()->getContext();
-  BasicBlock *ThenBlock = BasicBlock::Create(C, "", Head->getParent());
-  BranchInst *HeadNewTerm =
-    BranchInst::Create(/*ifTrue*/ThenBlock, /*ifFalse*/Tail, Cmp);
-  ReplaceInstWithInst(HeadOldTerm, HeadNewTerm);
 
-  BranchInst *CheckTerm = BranchInst::Create(Tail, ThenBlock);
-  return CheckTerm;
+  // Create three basic blocks, with the middle block empty, by splitting twice.
+  BasicBlock *Head = SplitBefore->getParent();
+  BasicBlock *Then = Head->splitBasicBlock(SplitBefore);
+  BasicBlock *Tail = Then->splitBasicBlock(SplitBefore);
+
+  TerminatorInst *HeadOldTerm = Head->getTerminator();
+  IRBuilder<>(HeadOldTerm).CreateCondBr(Cmp, Then, Tail);
+  HeadOldTerm->eraseFromParent();
+
+  return cast<BranchInst>(Then->getTerminator());
 }
 
 Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
@@ -387,28 +387,28 @@
   Value *Cmp = IRB.CreateICmpNE(ShadowValue, CmpVal);
 
   Instruction *CheckTerm = splitBlockAndInsertIfThen(Cmp);
-  IRBuilder<> IRB2(CheckTerm);
+  IRB.SetInsertPoint(CheckTerm);
 
   size_t Granularity = 1 << MappingScale;
   if (TypeSize < 8 * Granularity) {
     // Addr & (Granularity - 1)
-    Value *LastAccessedByte = IRB2.CreateAnd(
+    Value *LastAccessedByte = IRB.CreateAnd(
         AddrLong, ConstantInt::get(IntptrTy, Granularity - 1));
     // (Addr & (Granularity - 1)) + size - 1
     if (TypeSize / 8 > 1)
-      LastAccessedByte = IRB2.CreateAdd(
+      LastAccessedByte = IRB.CreateAdd(
           LastAccessedByte, ConstantInt::get(IntptrTy, TypeSize / 8 - 1));
     // (uint8_t) ((Addr & (Granularity-1)) + size - 1)
-    LastAccessedByte = IRB2.CreateIntCast(
+    LastAccessedByte = IRB.CreateIntCast(
         LastAccessedByte, IRB.getInt8Ty(), false);
     // ((uint8_t) ((Addr & (Granularity-1)) + size - 1)) >= ShadowValue
-    Value *Cmp2 = IRB2.CreateICmpSGE(LastAccessedByte, ShadowValue);
+    Value *Cmp2 = IRB.CreateICmpSGE(LastAccessedByte, ShadowValue);
 
     CheckTerm = splitBlockAndInsertIfThen(Cmp2);
+    IRB.SetInsertPoint(CheckTerm);
   }
 
-  IRBuilder<> IRB1(CheckTerm);
-  Instruction *Crash = generateCrashCode(IRB1, AddrLong, IsWrite, TypeSize);
+  Instruction *Crash = generateCrashCode(IRB, AddrLong, IsWrite, TypeSize);
   Crash->setDebugLoc(OrigIns->getDebugLoc());
   ReplaceInstWithInst(CheckTerm, new UnreachableInst(*C));
 }