[Darwin] Add a new -mstack-probe option and enable by default

[aemerson]

Summary

Add a new -mstack-probe and -mno-stack-probe option to enable the generation of stack probing functions on non-Windows platforms, if supported. This patch only enables this for Darwin.

[Gerolf]

It looks pretty straightforward, but I'd ask (at least) Duncan or Akira, and Matthias to review this more carefully.

-Gerolf

[ahatanak]

lib/CodeGen/BackendUtil.cpp

442

Is there a reason you can't use function attributes "probe-stack"="___chkstk_darwin" and "stack-probe-size"=4096 instead of setting a TargetOptions flag here? If you intend to use stack probing with LTO, I think you need function attributes. Also, it looks like that would simplify the changes made to X86 backend.

lib/Driver/ToolChains/Clang.cpp

3955

Just to confirm, is stack probing going to be enabled unconditionally on Darwin unless the user disables it with mno-stack-probe?

[aemerson]

lib/CodeGen/BackendUtil.cpp

442

I don't think there's any reason not to. Is it worth specifying the probe size itself given that it'll be a known fixed value? It could be misleading to give a probe size which only has a single valid value for Darwin.

lib/Driver/ToolChains/Clang.cpp

3955

Yes that's the intention. However on D40863 there's discussion that it might be better to restrict to newer Darwin targets.

[ahatanak]

lib/CodeGen/BackendUtil.cpp

442

If 4096B is the only valid size for Darwin and the default size is 4096B in the backend, you can just add attribute "probe-stack"="___chkstk_darwin" to the function. The backend can check the existence of the attribute and decide whether to enable stack-probing.

[dexonsmith]

Did this eventually go in?

[aemerson]

In D40864#1100492, @dexonsmith wrote:

Did this eventually go in?

No, this approach was superseded. I will upstream a new implementation in the near future.

include/clang/Driver/Options.td

 def mms_bitfields : Flag<["-"], "mms-bitfields">, Group<m_Group>, Flags<[CC1Option]>,
   HelpText<"Set the default structure layout to be compatible with the Microsoft compiler standard">;
 def mno_ms_bitfields : Flag<["-"], "mno-ms-bitfields">, Group<m_Group>,
   HelpText<"Do not set the default structure layout to be compatible with the Microsoft compiler standard">;
 def mstackrealign : Flag<["-"], "mstackrealign">, Group<m_Group>, Flags<[CC1Option]>,
   HelpText<"Force realign the stack at entry to every function">;
 def mstack_alignment : Joined<["-"], "mstack-alignment=">, Group<m_Group>, Flags<[CC1Option]>,
   HelpText<"Set the stack alignment">;
+def mstack_probe : Flag<["-"], "mstack-probe">, Group<m_Group>, Flags<[CC1Option]>,
+  HelpText<"Enable stack probing for non-Windows targets (if supported)">;
+def mno_stack_probe : Flag<["-"], "mno-stack-probe">, Group<m_Group>, Flags<[CC1Option]>,
+  HelpText<"Disable stack probing for non-Windows targets">;
 def mstack_probe_size : Joined<["-"], "mstack-probe-size=">, Group<m_Group>, Flags<[CC1Option]>,
   HelpText<"Set the stack probe size">;
 def mthread_model : Separate<["-"], "mthread-model">, Group<m_Group>, Flags<[CC1Option]>,
   HelpText<"The thread model to use, e.g. posix, single (posix by default)">, Values<"posix,single">;
 def meabi : Separate<["-"], "meabi">, Group<m_Group>, Flags<[CC1Option]>,
   HelpText<"Set EABI type, e.g. 4, 5 or gnu (default depends on triple)">, Values<"default,4,5,gnu">;
 
 def mno_constant_cfstrings : Flag<["-"], "mno-constant-cfstrings">, Group<m_Group>;

include/clang/Frontend/CodeGenOptions.def

CODEGENOPT(VerifyModule      , 1, 1) ///< Control whether the module should be run
                                      ///< through the LLVM Verifier.
 
 CODEGENOPT(StackRealignment  , 1, 0) ///< Control whether to force stack
                                      ///< realignment.
 CODEGENOPT(UseInitArray      , 1, 0) ///< Control whether to use .init_array or
                                      ///< .ctors.
 VALUE_CODEGENOPT(StackAlignment    , 32, 0) ///< Overrides default stack
                                             ///< alignment, if not 0.
+CODEGENOPT(StackProbe        , 1, 0) ///< Whether to enable stack probing for
+                                     ///< non-Windows targets.
 VALUE_CODEGENOPT(StackProbeSize    , 32, 4096) ///< Overrides default stack
                                                ///< probe size, even if 0.
 CODEGENOPT(DebugColumnInfo, 1, 0) ///< Whether or not to use column information
                                   ///< in debug info.
 
 CODEGENOPT(DebugTypeExtRefs, 1, 0) ///< Whether or not debug info should contain
                                    ///< external references to a PCH or module.
 

lib/CodeGen/BackendUtil.cpp

static void initTargetOptions(llvm::TargetOptions &Options,
   Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
   Options.FunctionSections = CodeGenOpts.FunctionSections;
   Options.DataSections = CodeGenOpts.DataSections;
   Options.UniqueSectionNames = CodeGenOpts.UniqueSectionNames;
   Options.EmulatedTLS = CodeGenOpts.EmulatedTLS;
   Options.DebuggerTuning = CodeGenOpts.getDebuggerTuning();
+  Options.EnableStackProbe = CodeGenOpts.StackProbe;
 
   if (CodeGenOpts.EnableSplitDwarf)
     Options.MCOptions.SplitDwarfFile = CodeGenOpts.SplitDwarfFile;
   Options.MCOptions.MCRelaxAll = CodeGenOpts.RelaxAll;
   Options.MCOptions.MCSaveTempLabels = CodeGenOpts.SaveTempLabels;
   Options.MCOptions.MCUseDwarfDirectory = !CodeGenOpts.NoDwarfDirectoryAsm;
   Options.MCOptions.MCNoExecStack = CodeGenOpts.NoExecStack;
   Options.MCOptions.MCIncrementalLinkerCompatible =

lib/Driver/ToolChains/Clang.cpp

if (Args.hasFlag(options::OPT_mstackrealign, options::OPT_mno_stackrealign,
                    false))
     CmdArgs.push_back(Args.MakeArgString("-mstackrealign"));
 
   if (Args.hasArg(options::OPT_mstack_alignment)) {
     StringRef alignment = Args.getLastArgValue(options::OPT_mstack_alignment);
     CmdArgs.push_back(Args.MakeArgString("-mstack-alignment=" + alignment));
   }
 
+  // On Darwin we can use stack probing provided by compiler-rt.
+  if (Args.hasFlag(options::OPT_mstack_probe, options::OPT_mno_stack_probe,
+                   RawTriple.isOSDarwin()))
+    CmdArgs.push_back("-mstack-probe");
+
   if (Args.hasArg(options::OPT_mstack_probe_size)) {
     StringRef Size = Args.getLastArgValue(options::OPT_mstack_probe_size);
 
     if (!Size.empty())
       CmdArgs.push_back(Args.MakeArgString("-mstack-probe-size=" + Size));
     else
       CmdArgs.push_back("-mstack-probe-size=0");
   }

lib/Frontend/CompilerInvocation.cpp

static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.StackRealignment = Args.hasArg(OPT_mstackrealign);
   if (Arg *A = Args.getLastArg(OPT_mstack_alignment)) {
     StringRef Val = A->getValue();
     unsigned StackAlignment = Opts.StackAlignment;
     Val.getAsInteger(10, StackAlignment);
     Opts.StackAlignment = StackAlignment;
   }
 
+  Opts.StackProbe = Args.hasArg(OPT_mstack_probe);
+
   if (Arg *A = Args.getLastArg(OPT_mstack_probe_size)) {
     StringRef Val = A->getValue();
     unsigned StackProbeSize = Opts.StackProbeSize;
     Val.getAsInteger(0, StackProbeSize);
     Opts.StackProbeSize = StackProbeSize;
   }
 
   if (Arg *A = Args.getLastArg(OPT_fobjc_dispatch_method_EQ)) {

test/Driver/generic-stack-probe.c

+// RUN: %clang -target x86_64-apple-darwin %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-DEFAULT
+// CHECK-DEFAULT: "-mstack-probe"
+
+// RUN: %clang -target x86_64-apple-darwin %s -mstack-probe -### 2>&1 | FileCheck %s --check-prefix=CHECK-PROBE
+// CHECK-PROBE: "-mstack-probe"
+
+// RUN: %clang -target x86_64-apple-darwin %s -mno-stack-probe -### 2>&1 | FileCheck %s --check-prefix=CHECK-NO-PROBE
+// CHECK-NO-PROBE-NOT: "-mno-stack-probe"

test/Driver/rewrite-legacy-objc.m

 // RUN: %clang -no-canonical-prefixes -target x86_64-apple-macosx10.7.0 -rewrite-legacy-objc %s -o - -### 2>&1 | \
 // RUN:   FileCheck -check-prefix=TEST0 %s
 // TEST0: clang{{.*}}" "-cc1"
 // TEST0: "-rewrite-objc"
 // FIXME: CHECK-NOT is broken somehow, it doesn't work here. Check adjacency instead.
-// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx-fragile" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-mstack-probe" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx-fragile" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
 // TEST0: rewrite-legacy-objc.m"
 // RUN: %clang -no-canonical-prefixes -target i386-apple-macosx10.9.0 -rewrite-legacy-objc %s -o - -### 2>&1 | \
 // RUN:   FileCheck -check-prefix=TEST1 %s
 // RUN: %clang -no-canonical-prefixes -target i386-apple-macosx10.6.0 -rewrite-legacy-objc %s -o - -### 2>&1 | \
 // RUN:   FileCheck -check-prefix=TEST2 %s
-// TEST1: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx-fragile" "-fobjc-subscripting-legacy-runtime" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
-// TEST2: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx-fragile" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST1: "-fmessage-length" "0" "-stack-protector" "1" "-mstack-probe" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx-fragile" "-fobjc-subscripting-legacy-runtime" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST2: "-fmessage-length" "0" "-stack-protector" "1" "-mstack-probe" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx-fragile" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"

test/Driver/rewrite-objc.m

 // RUN: %clang -no-canonical-prefixes -target x86_64-apple-macosx10.7.0 -rewrite-objc %s -o - -### 2>&1 | \
 // RUN:   FileCheck -check-prefix=TEST0 %s
 // TEST0: clang{{.*}}" "-cc1"
 // TEST0: "-rewrite-objc"
 // FIXME: CHECK-NOT is broken somehow, it doesn't work here. Check adjacency instead.
-// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-mstack-probe" "-fblocks" "-fencode-extended-block-signature" "-fobjc-runtime=macosx" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"