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.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@91198 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/LangOptions.h

@@ -92,6 +92,7 @@ public:
 
   unsigned ElideConstructors : 1; // Whether C++ copy constructors should be
                                   // elided if possible.
+  unsigned CatchUndefined     :1; // Generate code to check for undefined ops.
 private:
   unsigned GC : 2;                // Objective-C Garbage Collection modes.  We
                                   // declare this enum as unsigned because MSVC
@@ -160,6 +161,7 @@ public:
 
     CharIsSigned = 1;
     ShortWChar = 0;
+    CatchUndefined = 0;
   }
 
   GCMode getGCMode() const { return (GCMode) GC; }

include/clang/Driver/CC1Options.td

@@ -105,6 +105,8 @@ def disable_llvm_optzns : Flag<"-disable-llvm-optzns">,
 def disable_red_zone : Flag<"-disable-red-zone">,
   HelpText<"Do not emit code that uses the red zone.">;
 def g : Flag<"-g">, HelpText<"Generate source level debug information">;
+def fcatch_undefined_behavior : Flag<"-fcatch-undefined-behavior">,
+    HelpText<"Generate runtime checks for undefined behavior.">;
 def fno_common : Flag<"-fno-common">,
   HelpText<"Compile common globals like normal definitions">;
 def no_implicit_float : Flag<"-no-implicit-float">,

include/clang/Driver/Options.td

@@ -236,6 +236,8 @@ def fbootclasspath_EQ : Joined<"-fbootclasspath=">, Group<f_Group>;
 def fbuiltin_strcat : Flag<"-fbuiltin-strcat">, Group<f_Group>;
 def fbuiltin_strcpy : Flag<"-fbuiltin-strcpy">, Group<f_Group>;
 def fbuiltin : Flag<"-fbuiltin">, Group<f_Group>;
+def fcatch_undefined_behavior : Flag<"-fcatch-undefined-behavior">,
+    Group<f_Group>, HelpText<"Generate runtime checks for undefined behavior.">;
 def fclasspath_EQ : Joined<"-fclasspath=">, Group<f_Group>;
 def fcolor_diagnostics : Flag<"-fcolor-diagnostics">, Group<f_Group>;
 def fcommon : Flag<"-fcommon">, Group<f_Group>;

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;

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 {

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();
 };
 
 

lib/Driver/Tools.cpp

@@ -895,6 +895,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   }
 
   // Forward -f (flag) options which we can pass directly.
+  Args.AddLastArg(CmdArgs, options::OPT_fcatch_undefined_behavior);
   Args.AddLastArg(CmdArgs, options::OPT_femit_all_decls);
   Args.AddLastArg(CmdArgs, options::OPT_ffreestanding);
   Args.AddLastArg(CmdArgs, options::OPT_fheinous_gnu_extensions);

lib/Frontend/CompilerInvocation.cpp

@@ -447,6 +447,8 @@ static void LangOptsToArgs(const LangOptions &Opts,
     Res.push_back("-fno-operator-names");
   if (Opts.PascalStrings)
     Res.push_back("-fpascal-strings");
+  if (Opts.CatchUndefined)
+    Res.push_back("-fcatch-undefined-behavior");
   if (Opts.WritableStrings)
     Res.push_back("-fwritable-strings");
   if (!Opts.LaxVectorConversions)
@@ -1151,6 +1153,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args,
   Opts.ObjCConstantStringClass = getLastArgValue(Args,
                                                  OPT_fconstant_string_class);
   Opts.ObjCNonFragileABI = Args.hasArg(OPT_fobjc_nonfragile_abi);
+  Opts.CatchUndefined = Args.hasArg(OPT_fcatch_undefined_behavior);
   Opts.EmitAllDecls = Args.hasArg(OPT_femit_all_decls);
   Opts.PICLevel = getLastArgIntValue(Args, OPT_pic_level, 0, Diags);
   Opts.Static = Args.hasArg(OPT_static_define);

lib/Frontend/PCHReader.cpp

@@ -116,6 +116,7 @@ PCHValidator::ReadLanguageOptions(const LangOptions &LangOpts) {
                           diag::warn_pch_stack_protector);
   PARSE_LANGOPT_BENIGN(InstantiationDepth);
   PARSE_LANGOPT_IMPORTANT(OpenCL, diag::warn_pch_opencl);
+  PARSE_LANGOPT_BENIGN(CatchUndefined);
   PARSE_LANGOPT_IMPORTANT(ElideConstructors, diag::warn_pch_elide_constructors);
 #undef PARSE_LANGOPT_IRRELEVANT
 #undef PARSE_LANGOPT_BENIGN
@@ -1719,6 +1720,8 @@ bool PCHReader::ParseLanguageOptions(
     ++Idx;
     PARSE_LANGOPT(InstantiationDepth);
     PARSE_LANGOPT(OpenCL);
+    PARSE_LANGOPT(CatchUndefined);
+    // FIXME: Missing ElideConstructors?!
   #undef PARSE_LANGOPT
 
     return Listener->ReadLanguageOptions(LangOpts);

lib/Frontend/PCHWriter.cpp

@@ -781,6 +781,7 @@ void PCHWriter::WriteLanguageOptions(const LangOptions &LangOpts) {
   Record.push_back(LangOpts.getStackProtectorMode());
   Record.push_back(LangOpts.InstantiationDepth);
   Record.push_back(LangOpts.OpenCL);
+  Record.push_back(LangOpts.CatchUndefined);
   Record.push_back(LangOpts.ElideConstructors);
   Stream.EmitRecord(pch::LANGUAGE_OPTIONS, Record);
 }