Implement runtime checks for undefined behavior. WIP.

This implements a new flag -fcatch-undefined-behavior.  The flag turns
on additional runtime checks for:

  T a[I];

  a[i]    abort when i < 0 or i >= I.

Future stuff includes shifts by >= bitwidth amounts.

llvm-svn: 91198

3 files changed, 69 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 70fa004de85..722ec868f59 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -1012,6 +1012,36 @@ LValue CodeGenFunction::EmitPredefinedLValue(const PredefinedExpr *E) {
   }
 }
 
+static llvm::Constant *getAbortFn(CodeGenFunction &CGF) {
+  // void abort();
+
+  const llvm::FunctionType *FTy =
+    llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()), false);
+
+  return CGF.CGM.CreateRuntimeFunction(FTy, "abort");
+}
+
+llvm::BasicBlock*CodeGenFunction::getAbortBB() {
+  if (AbortBB)
+    return AbortBB;
+
+  llvm::BasicBlock *Cont = 0;
+  if (HaveInsertPoint()) {
+    Cont = createBasicBlock("cont");
+    EmitBranch(Cont);
+  }
+  AbortBB = createBasicBlock("abort");
+  EmitBlock(AbortBB);
+  llvm::CallInst *AbortCall = Builder.CreateCall(getAbortFn(*this));
+  AbortCall->setDoesNotReturn();
+  AbortCall->setDoesNotThrow();
+  Builder.CreateUnreachable();
+
+  if (Cont)
+    EmitBlock(Cont);
+  return AbortBB;
+}
+
 LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E) {
   // The index must always be an integer, which is not an aggregate.  Emit it.
   llvm::Value *Idx = EmitScalarExpr(E->getIdx());
@@ -1040,6 +1070,37 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E) {
                             llvm::IntegerType::get(VMContext, LLVMPointerWidth),
                                 IdxSigned, "idxprom");
 
+  if (CatchUndefined) {
+    if (const ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(E->getBase())) {
+      if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(ICE->getSubExpr())) {
+        if (ICE->getCastKind() == CastExpr::CK_ArrayToPointerDecay) {
+          if (const ConstantArrayType *CAT
+              = getContext().getAsConstantArrayType(DRE->getType())) {
+            llvm::APInt Size = CAT->getSize();
+            llvm::BasicBlock *Cont = createBasicBlock("cont");
+            if (IdxSigned) {
+              Builder.CreateCondBr(Builder.CreateICmpSGE(Idx,
+                                     llvm::ConstantInt::get(Idx->getType(), 0)),
+                                   Cont, getAbortBB());
+              EmitBlock(Cont);
+              Cont = createBasicBlock("cont");
+              Builder.CreateCondBr(Builder.CreateICmpSLT(Idx,
+                                  llvm::ConstantInt::get(Idx->getType(), Size)),
+                                   Cont, getAbortBB());
+              EmitBlock(Cont);
+            } else {
+              llvm::BasicBlock *Cont = createBasicBlock("cont");
+              Builder.CreateCondBr(Builder.CreateICmpULT(Idx,
+                                  llvm::ConstantInt::get(Idx->getType(), Size)),
+                                   Cont, getAbortBB());
+              EmitBlock(Cont);
+            }
+          }
+        }
+      }
+    }
+  }
+
   // We know that the pointer points to a type of the correct size, unless the
   // size is a VLA or Objective-C interface.
   llvm::Value *Address = 0;
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 26964529ea6..db604f63b18 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -32,10 +32,11 @@ CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
     SwitchInsn(0), CaseRangeBlock(0), InvokeDest(0),
     CXXThisDecl(0), CXXVTTDecl(0),
     ConditionalBranchLevel(0), TerminateHandler(0),
-    UniqueAggrDestructorCount(0) {
+    UniqueAggrDestructorCount(0), AbortBB(0) {
   LLVMIntTy = ConvertType(getContext().IntTy);
   LLVMPointerWidth = Target.getPointerWidth(0);
   Exceptions = getContext().getLangOptions().Exceptions;
+  CatchUndefined = getContext().getLangOptions().CatchUndefined;
 }
 
 ASTContext &CodeGenFunction::getContext() const {
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 1ddfa6d6c02..8820e6ec8b7 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -108,6 +108,7 @@ public:
   uint32_t LLVMPointerWidth;
 
   bool Exceptions;
+  bool CatchUndefined;
 public:
   /// ObjCEHValueStack - Stack of Objective-C exception values, used for
   /// rethrows.
@@ -1266,6 +1267,11 @@ private:
                                     ArgType));
     }
   }
+
+  llvm::BasicBlock *AbortBB;
+  /// getAbortBB - Create a basic block that will call abort.  We'll generate
+  /// a branch around the created basic block as necessary.
+  llvm::BasicBlock* getAbortBB();
 };