Driver: enable support for -fsanitize=cfi on Windows.

[pcc]

Summary

There are known issues, but the current implementation is good enough for
the check-cfi test suite.

[samsonov]

LGTM

lib/Driver/MSVCToolChain.cpp

else
           (Twine("msvc") + MSVT.getAsString() + Twine('-') + ObjFmt).str());
   }
   return Triple.getTriple();
 }
 
 SanitizerMask MSVCToolChain::getSupportedSanitizers() const {
   SanitizerMask Res = ToolChain::getSupportedSanitizers();
   Res |= SanitizerKind::Address;
-  // CFI checks are not implemented for MSVC ABI for now.
-  Res &= ~SanitizerKind::CFI;
-  Res &= ~SanitizerKind::CFICastStrict;
   return Res;
 }

lib/Driver/SanitizerArgs.cpp

D.Diag(diag::err_drv_argument_only_allowed_with)
         << lastArgumentForMask(D, Args, Kinds & NeedsLTO) << "-flto";
   }
 
   // Report error if there are non-trapping sanitizers that require
   // c++abi-specific  parts of UBSan runtime, and they are not provided by the
   // toolchain. We don't have a good way to check the latter, so we just
   // check if the toolchan supports vptr.
   if (~Supported & Vptr) {
-    if (SanitizerMask KindsToDiagnose =
-            Kinds & ~TrappingKinds & NeedsUbsanCxxRt) {
+    SanitizerMask KindsToDiagnose = Kinds & ~TrappingKinds & NeedsUbsanCxxRt;
+    // The runtime library supports the Microsoft C++ ABI, but only well enough
+    // for CFI. FIXME: Remove this once we support vptr on Windows.
+    if (TC.getTriple().isOSWindows())
+      KindsToDiagnose &= ~CFI;
+    if (KindsToDiagnose) {
       SanitizerSet S;
       S.Mask = KindsToDiagnose;
       D.Diag(diag::err_drv_unsupported_opt_for_target)
           << ("-fno-sanitize-trap=" + toString(S)) << TC.getTriple().str();
       Kinds &= ~KindsToDiagnose;
     }
   }
 

test/Driver/fsanitize.c

 // 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'
 
 // RUN: %clang -target x86_64-apple-darwin10 -mmacosx-version-min=10.7 -flto -fsanitize=cfi-vcall -fno-sanitize-trap=cfi -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-NOTRAP-OLD-MACOS
 // CHECK-CFI-NOTRAP-OLD-MACOS: error: unsupported option '-fno-sanitize-trap=cfi-vcall' for target 'x86_64-apple-darwin10'
 
+// RUN: %clang -target x86_64-pc-win32 -flto -fsanitize=cfi-vcall -fno-sanitize-trap=cfi -c %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-CFI-NOTRAP-WIN
+// CHECK-CFI-NOTRAP-WIN: -emit-llvm-bc
+// CHECK-CFI-NOTRAP-WIN-NOT: -fsanitize-trap=cfi
+
 // RUN: %clang_cl -fsanitize=address -c -MDd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -MTd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -LDd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -MD -MDd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -MT -MTd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // RUN: %clang_cl -fsanitize=address -c -LD -LDd -### -- %s 2>&1 | FileCheck %s -check-prefix=CHECK-ASAN-DEBUGRTL
 // CHECK-ASAN-DEBUGRTL: error: invalid argument
 // CHECK-ASAN-DEBUGRTL: not allowed with '-fsanitize=address'