Now with the patch, sorry..
Nuno
Citando Nuno Lopes <[email protected]>:
Hi,
I would like to add a new option to clang: -fbounds-checking. It emits
run-time bounds checks for array/pointers dereferencing based on
LLVM's object size built-in. The code to emit the checks is already in
clang; it's just a matter of wiring the flag.
The other change is to make -fcatch-undefined-behavior imply
-fbounds-checking (so that it keeps doing these kinds of checks).
This flag supports an additional integer parameter to control the
amount of run-time performance penalty you're willing to afford. For
example, -fbounds-checking=1 will only resolve stuff at compile-time,
while at level 2 it can defer some stuff to run-time. This will come
in a separate patch to LLVM.
Comments, ideas, etc?
Thanks,
Nuno
Index: include/clang/Basic/LangOptions.def
===================================================================
--- include/clang/Basic/LangOptions.def (revision 156311)
+++ include/clang/Basic/LangOptions.def (working copy)
@@ -157,6 +157,7 @@
"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++")
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td (revision 156311)
+++ include/clang/Driver/Options.td (working copy)
@@ -315,6 +315,9 @@
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">,
+ HelpText<"Enable run-time bounds checks.">, Group<f_Group>;
+def Wbounds_checking_EQ : Joined<"-fbounds-checking=">, 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>;
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp (revision 156311)
+++ lib/Frontend/CompilerInvocation.cpp (working copy)
@@ -675,6 +675,8 @@
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 +1955,9 @@
Opts.ObjCNonFragileABI2 = true;
Opts.ObjCDefaultSynthProperties =
Args.hasArg(OPT_fobjc_default_synthesize_properties);
- Opts.CatchUndefined = Args.hasArg(OPT_fcatch_undefined_behavior);
+ Opts.BoundsChecking = Args.getLastArgIntValue(OPT_fbounds_checking, 0,
Diags);
+ if ((Opts.CatchUndefined = Args.hasArg(OPT_fcatch_undefined_behavior)))
+ Opts.BoundsChecking = 5;
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);
Index: lib/CodeGen/CodeGenFunction.cpp
===================================================================
--- lib/CodeGen/CodeGenFunction.cpp (revision 156311)
+++ lib/CodeGen/CodeGenFunction.cpp (working copy)
@@ -41,6 +41,7 @@
CXXVTTValue(0), OutermostConditional(0), TerminateLandingPad(0),
TerminateHandler(0), TrapBB(0) {
+ BoundsChecking = getContext().getLangOpts().BoundsChecking;
CatchUndefined = getContext().getLangOpts().CatchUndefined;
CGM.getCXXABI().getMangleContext().startNewFunction();
}
Index: lib/CodeGen/CGExpr.cpp
===================================================================
--- lib/CodeGen/CGExpr.cpp (revision 156311)
+++ lib/CodeGen/CGExpr.cpp (working copy)
@@ -517,7 +517,7 @@
}
void CodeGenFunction::EmitCheck(llvm::Value *Address, unsigned Size) {
- if (!CatchUndefined)
+ if (BoundsChecking <= 0)
return;
// This needs to be to the standard address space.
Index: lib/CodeGen/CodeGenFunction.h
===================================================================
--- lib/CodeGen/CodeGenFunction.h (revision 156311)
+++ lib/CodeGen/CodeGenFunction.h (working copy)
@@ -591,6 +591,11 @@
/// 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.
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