add -fbounds-checking option.

When enabled, clang generates bounds checks for array and pointers dereferences. Work to follow in LLVM's backend.

OK'ed by Chad; thanks for the review.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156431 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/LangOptions.def

@@ -157,6 +157,7 @@ BENIGN_LANGOPT(ConstexprCallDepth, 32, 512,
                "maximum constexpr call depth")
 BENIGN_LANGOPT(NumLargeByValueCopy, 32, 0, 
         "if non-zero, warn about parameter or return Warn if parameter/return value is larger in bytes than this setting. 0 is no check.")
+BENIGN_LANGOPT(BoundsChecking , 8, 0, "if non-zero, add run-time bounds checking code")
 VALUE_LANGOPT(MSCVersion, 32, 0, 
               "version of Microsoft Visual C/C++")
 

include/clang/Driver/Options.td

@@ -315,6 +315,10 @@ def fblocks : Flag<"-fblocks">, Group<f_Group>, Flags<[CC1Option]>,
 def fbootclasspath_EQ : Joined<"-fbootclasspath=">, Group<f_Group>;
 def fborland_extensions : Flag<"-fborland-extensions">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Accept non-standard constructs supported by the Borland compiler">;
+def fbounds_checking : Flag<"-fbounds-checking">, Group<f_Group>,
+  HelpText<"Enable run-time bounds checks.">;
+def fbounds_checking_EQ : Joined<"-fbounds-checking=">, Flags<[CC1Option]>,
+  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>;

lib/CodeGen/CGExpr.cpp

@@ -517,7 +517,7 @@ unsigned CodeGenFunction::getAccessedFieldNo(unsigned Idx,
 }
 
 void CodeGenFunction::EmitCheck(llvm::Value *Address, unsigned Size) {
-  if (!CatchUndefined)
+  if (BoundsChecking <= 0)
     return;
 
   // This needs to be to the standard address space.

lib/CodeGen/CodeGenFunction.cpp

@@ -41,6 +41,7 @@ CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
     CXXVTTValue(0), OutermostConditional(0), TerminateLandingPad(0),
     TerminateHandler(0), TrapBB(0) {
 
+  BoundsChecking = getContext().getLangOpts().BoundsChecking;
   CatchUndefined = getContext().getLangOpts().CatchUndefined;
   CGM.getCXXABI().getMangleContext().startNewFunction();
 }

lib/CodeGen/CodeGenFunction.h

@@ -591,6 +591,11 @@ public:
   /// we prefer to insert allocas.
   llvm::AssertingVH<llvm::Instruction> AllocaInsertPt;
 
+  /// BoundsChecking - Emit run-time bounds checks. Higher values mean
+  /// potentially higher performance penalties.
+  unsigned char BoundsChecking;
+
+  /// CatchUndefined - Emit run-time checks to catch undefined behaviors.
   bool CatchUndefined;
 
   /// In ARC, whether we should autorelease the return value.

lib/Driver/Tools.cpp

@@ -2025,6 +2025,15 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       CmdArgs.push_back("-Wlarge-by-value-copy=64"); // default value
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_fbounds_checking,
+                               options::OPT_fbounds_checking_EQ)) {
+    if (A->getNumValues()) {
+      StringRef val = A->getValue(Args);
+      CmdArgs.push_back(Args.MakeArgString("-fbounds-checking=" + val));
+    } else
+      CmdArgs.push_back("-fbounds-checking=1");
+  }
+
   if (Args.hasArg(options::OPT__relocatable_pch))
     CmdArgs.push_back("-relocatable-pch");
 

lib/Frontend/CompilerInvocation.cpp

@@ -675,6 +675,8 @@ static void LangOptsToArgs(const LangOptions &Opts, ToArgsList &Res) {
     Res.push_back("-fno-operator-names");
   if (Opts.PascalStrings)
     Res.push_back("-fpascal-strings");
+  if (Opts.BoundsChecking > 0)
+    Res.push_back("-fbounds-checking=" + llvm::utostr(Opts.BoundsChecking));
   if (Opts.CatchUndefined)
     Res.push_back("-fcatch-undefined-behavior");
   if (Opts.AddressSanitizer)
@@ -1953,7 +1955,11 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
     Opts.ObjCNonFragileABI2 = true;
   Opts.ObjCDefaultSynthProperties =
     Args.hasArg(OPT_fobjc_default_synthesize_properties);
-  Opts.CatchUndefined = Args.hasArg(OPT_fcatch_undefined_behavior);
+  Opts.BoundsChecking = 0;
+  if ((Opts.CatchUndefined = Args.hasArg(OPT_fcatch_undefined_behavior)))
+    Opts.BoundsChecking = 5;
+  Opts.BoundsChecking = Args.getLastArgIntValue(OPT_fbounds_checking_EQ,
+                                                Opts.BoundsChecking, Diags);
   Opts.EmitAllDecls = Args.hasArg(OPT_femit_all_decls);
   Opts.PackStruct = Args.getLastArgIntValue(OPT_fpack_struct_EQ, 0, Diags);
   Opts.PICLevel = Args.getLastArgIntValue(OPT_pic_level, 0, Diags);

test/Driver/bounds-checking.c

@@ -0,0 +1,7 @@
+// RUN: %clang -target x86_64-apple-darwin10 -fbounds-checking -### -fsyntax-only %s 2> %t
+// RUN: FileCheck < %t %s
+// RUN: %clang -target x86_64-apple-darwin10 -fbounds-checking=3 -### -fsyntax-only %s 2> %t
+// RUN: FileCheck -check-prefix=CHECK2 < %t %s
+
+// CHECK: "-fbounds-checking=1"
+// CHECK2: "-fbounds-checking=3"