[CFI] Require -flto instead of implying it.

Summary:
This is unfortunate, but would let us land http://reviews.llvm.org/D10467,
that makes ToolChains responsible for computing the set of sanitizers
they support.

Unfortunately, Darwin ToolChains doesn't know about actual OS they
target until ToolChain::TranslateArgs() is called. In particular, it
means we won't be able to construct SanitizerArgs for these ToolChains
before that.

This change removes SanitizerArgs::needsLTO() method, so that now
ToolChain::IsUsingLTO(), which is called very early, doesn't need
SanitizerArgs to implement this method.

Docs and test cases are updated accordingly. See
https://llvm.org/bugs/show_bug.cgi?id=23539, which describes why we
start all these.

Test Plan: regression test suite

Reviewers: pcc

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D10560

llvm-svn: 240170

clang/docs/ControlFlowIntegrity.rst

@@ -20,8 +20,8 @@ program's control flow. These schemes have been optimized for performance,
 allowing developers to enable them in release builds.
 
 To enable Clang's available CFI schemes, use the flag ``-fsanitize=cfi``.
-As currently implemented, CFI relies on link-time optimization (LTO); the CFI
-schemes imply ``-flto``, and the linker used must support LTO, for example
+As currently implemented, CFI relies on link-time optimization (LTO); so it is
+required to specify ``-flto``, and the linker used must support LTO, for example
 via the `gold plugin`_. To allow the checks to be implemented efficiently,
 the program must be structured such that certain object files are compiled
 with CFI enabled, and are statically linked into the program. This may

clang/docs/UsersManual.rst

@@ -976,7 +976,7 @@ are listed below.
    -  ``-fsanitize=dataflow``: :doc:`DataFlowSanitizer`, a general data
       flow analysis.
    -  ``-fsanitize=cfi``: :doc:`control flow integrity <ControlFlowIntegrity>`
-      checks. Implies ``-flto``.
+      checks. Requires ``-flto``.
    -  ``-fsanitize=safe-stack``: :doc:`safe stack <SafeStack>`
       protection against stack-based memory corruption errors.
 
@@ -991,13 +991,13 @@ are listed below.
    -  ``-fsanitize=cfi-cast-strict``: Enables :ref:`strict cast checks
       <cfi-strictness>`.
    -  ``-fsanitize=cfi-derived-cast``: Base-to-derived cast to the wrong
-      dynamic type. Implies ``-flto``.
+      dynamic type. Requires ``-flto``.
    -  ``-fsanitize=cfi-unrelated-cast``: Cast from ``void*`` or another
-      unrelated type to the wrong dynamic type. Implies ``-flto``.
+      unrelated type to the wrong dynamic type. Requires ``-flto``.
    -  ``-fsanitize=cfi-nvcall``: Non-virtual call via an object whose vptr is of
-      the wrong dynamic type. Implies ``-flto``.
+      the wrong dynamic type. Requires ``-flto``.
    -  ``-fsanitize=cfi-vcall``: Virtual call via an object whose vptr is of the
-      wrong dynamic type. Implies ``-flto``.
+      wrong dynamic type. Requires ``-flto``.
    -  ``-fsanitize=enum``: Load of a value of an enumerated type which
       is not in the range of representable values for that enumerated
       type.

clang/include/clang/Driver/Driver.h

@@ -402,7 +402,7 @@ public:
   /// handle this action.
   bool ShouldUseClangCompiler(const JobAction &JA) const;
 
-  bool IsUsingLTO(const ToolChain &TC, const llvm::opt::ArgList &Args) const;
+  bool IsUsingLTO(const llvm::opt::ArgList &Args) const;
 
 private:
   /// \brief Retrieves a ToolChain for a particular target triple.

clang/include/clang/Driver/SanitizerArgs.h

@@ -53,7 +53,6 @@ class SanitizerArgs {
 
   bool requiresPIE() const;
   bool needsUnwindTables() const;
-  bool needsLTO() const;
   bool linkCXXRuntimes() const { return LinkCXXRuntimes; }
   void addArgs(const llvm::opt::ArgList &Args,
                llvm::opt::ArgStringList &CmdArgs) const;

clang/lib/Driver/Driver.cpp

@@ -1362,7 +1362,7 @@ Driver::ConstructPhaseAction(const ToolChain &TC, const ArgList &Args,
                                                types::TY_LLVM_BC);
   }
   case phases::Backend: {
-    if (IsUsingLTO(TC, Args)) {
+    if (IsUsingLTO(Args)) {
       types::ID Output =
         Args.hasArg(options::OPT_S) ? types::TY_LTO_IR : types::TY_LTO_BC;
       return llvm::make_unique<BackendJobAction>(std::move(Input), Output);
@@ -1383,14 +1383,8 @@ Driver::ConstructPhaseAction(const ToolChain &TC, const ArgList &Args,
   llvm_unreachable("invalid phase in ConstructPhaseAction");
 }
 
-bool Driver::IsUsingLTO(const ToolChain &TC, const ArgList &Args) const {
-  if (TC.getSanitizerArgs().needsLTO())
-    return true;
-
-  if (Args.hasFlag(options::OPT_flto, options::OPT_fno_lto, false))
-    return true;
-
-  return false;
+bool Driver::IsUsingLTO(const ArgList &Args) const {
+  return Args.hasFlag(options::OPT_flto, options::OPT_fno_lto, false);
 }
 
 void Driver::BuildJobs(Compilation &C) const {

clang/lib/Driver/SanitizerArgs.cpp

@@ -188,10 +188,6 @@ bool SanitizerArgs::needsUnwindTables() const {
   return Sanitizers.Mask & NeedsUnwindTables;
 }
 
-bool SanitizerArgs::needsLTO() const {
-  return Sanitizers.Mask & NeedsLTO;
-}
-
 void SanitizerArgs::clear() {
   Sanitizers.clear();
   RecoverableSanitizers.clear();
@@ -301,6 +297,12 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
     Kinds &= ~Vptr;
   }
 
+  // Check that LTO is enabled if we need it.
+  if ((Kinds & NeedsLTO) && !D.IsUsingLTO(Args)) {
+    D.Diag(diag::err_drv_argument_only_allowed_with)
+        << lastArgumentForMask(D, Args, Kinds & NeedsLTO) << "-flto";
+  }
+
   // Warn about incompatible groups of sanitizers.
   std::pair<SanitizerMask, SanitizerMask> IncompatibleGroups[] = {
       std::make_pair(Address, Thread), std::make_pair(Address, Memory),

clang/lib/Driver/Tools.cpp

@@ -6038,7 +6038,7 @@ void cloudabi::Link::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddAllArgs(CmdArgs, options::OPT_Z_Flag);
   Args.AddAllArgs(CmdArgs, options::OPT_r);
 
-  if (D.IsUsingLTO(ToolChain, Args))
+  if (D.IsUsingLTO(Args))
     AddGoldPlugin(ToolChain, Args, CmdArgs);
 
   AddLinkerInputs(ToolChain, Inputs, Args, CmdArgs);
@@ -6189,8 +6189,7 @@ void darwin::Link::AddLinkArgs(Compilation &C,
   // If we are using LTO, then automatically create a temporary file path for
   // the linker to use, so that it's lifetime will extend past a possible
   // dsymutil step.
-  if (Version[0] >= 116 && D.IsUsingLTO(getToolChain(), Args) &&
-      NeedsTempPath(Inputs)) {
+  if (Version[0] >= 116 && D.IsUsingLTO(Args) && NeedsTempPath(Inputs)) {
     const char *TmpPath = C.getArgs().MakeArgString(
       D.GetTemporaryPath("cc", types::getTypeTempSuffix(types::TY_Object)));
     C.addTempFile(TmpPath);
@@ -7226,7 +7225,7 @@ void freebsd::Link::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddAllArgs(CmdArgs, options::OPT_Z_Flag);
   Args.AddAllArgs(CmdArgs, options::OPT_r);
 
-  if (D.IsUsingLTO(getToolChain(), Args))
+  if (D.IsUsingLTO(Args))
     AddGoldPlugin(ToolChain, Args, CmdArgs);
 
   bool NeedsSanitizerDeps = addSanitizerRuntimes(ToolChain, Args, CmdArgs);
@@ -8086,7 +8085,7 @@ void gnutools::Link::ConstructJob(Compilation &C, const JobAction &JA,
   for (const auto &Path : Paths)
     CmdArgs.push_back(Args.MakeArgString(StringRef("-L") + Path));
 
-  if (D.IsUsingLTO(getToolChain(), Args))
+  if (D.IsUsingLTO(Args))
     AddGoldPlugin(ToolChain, Args, CmdArgs);
 
   if (Args.hasArg(options::OPT_Z_Xlinker__no_demangle))

clang/test/Driver/fsanitize.c

@@ -202,17 +202,20 @@
 // RUN: %clang -target x86_64-apple-darwin10 -fsanitize=function -fsanitize=undefined %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-FSAN-UBSAN-DARWIN
 // CHECK-FSAN-UBSAN-DARWIN: unsupported option '-fsanitize=function' for target 'x86_64-apple-darwin10'
 
-// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI
-// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-derived-cast -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-DCAST
-// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-unrelated-cast -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-UCAST
-// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-nvcall -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-NVCALL
-// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-vcall -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-VCALL
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi -flto -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-derived-cast -flto -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-DCAST
+// RUN: %clang -target x86_64-linux-gnu -fsanitize=cfi-unrelated-cast -flto -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-UCAST
+// RUN: %clang -target x86_64-linux-gnu -flto -fsanitize=cfi-nvcall -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-NVCALL
+// RUN: %clang -target x86_64-linux-gnu -flto -fsanitize=cfi-vcall -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-VCALL
 // CHECK-CFI: -emit-llvm-bc{{.*}}-fsanitize=cfi-derived-cast,cfi-unrelated-cast,cfi-nvcall,cfi-vcall
 // CHECK-CFI-DCAST: -emit-llvm-bc{{.*}}-fsanitize=cfi-derived-cast
 // CHECK-CFI-UCAST: -emit-llvm-bc{{.*}}-fsanitize=cfi-unrelated-cast
 // CHECK-CFI-NVCALL: -emit-llvm-bc{{.*}}-fsanitize=cfi-nvcall
 // CHECK-CFI-VCALL: -emit-llvm-bc{{.*}}-fsanitize=cfi-vcall
 
+// RUN: %clang -target x86_64-linux-gnu -flto -fsanitize=cfi-derived-cast -fno-lto -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-NOLTO
+// CHECK-CFI-NOLTO: '-fsanitize=cfi-derived-cast' only allowed with '-flto'
+
 // RUN: %clang -target x86_64-linux-gnu -fsanitize-trap=address -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-ASAN-TRAP
 // CHECK-ASAN-TRAP: error: unsupported argument 'address' to option '-fsanitize-trap'