Revert r369402 "win: Enable /Zc:twoPhase by default if targeting MSVC 2017 update 3 or newer"

This broke compiling some ASan tests with never versions of MSVC/the Win
SDK, see https://crbug.com/996675

> MSVC 2017 update 3 (_MSC_VER 1911) enables /Zc:twoPhase by default, and
> so should clang-cl:
> https://docs.microsoft.com/en-us/cpp/build/reference/zc-twophase
>
> clang-cl takes the MSVC version it emulates from the -fmsc-version flag,
> or if that's not passed it tries to check what the installed version of
> MSVC is and uses that, and failing that it uses a default version that's
> currently 1911. So this changes the default if no -fmsc-version flag is
> passed and no installed MSVC is detected. (It also changes the default
> if -fmsc-version is passed or MSVC is detected, and either indicates
> _MSC_VER >= 1911.)
>
> As mentioned in the MSDN article, the Windows SDK header files in
> version 10.0.15063.0 (Creators Update or Redstone 2) and earlier
> versions do not work correctly with /Zc:twoPhase. If you need to use
> these old SDKs with a new clang-cl, explicitly pass /Zc:twoPhase- to get
> the old behavior.
>
> Fixes PR43032.
>
> Differential Revision: https://reviews.llvm.org/D66394

llvm-svn: 369647

1 files changed, 5 insertions, 7 deletions

diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index c0f914bf989..690d4fa3fa4 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4883,14 +4883,12 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                     !IsWindowsMSVC || IsMSVC2015Compatible))
     CmdArgs.push_back("-fno-threadsafe-statics");
 
-  // -fno-delayed-template-parsing is default, except when targeting MSVC
-  // earlier than MSVC 2017 15.3 (_MSC_VER 1911).  Windows SDK versions
-  // 10.0.15063.0 (Creators Update or Redstone 2) and earlier require this to
-  // parse.
-  bool IsMSVCBefore2017Update3 = !MSVT.empty() && MSVT < VersionTuple(19, 11);
+  // -fno-delayed-template-parsing is default, except when targeting MSVC.
+  // Many old Windows SDK versions require this to parse.
+  // FIXME: MSVC introduced /Zc:twoPhase- to disable this behavior in their
+  // compiler. We should be able to disable this by default at some point.
   if (Args.hasFlag(options::OPT_fdelayed_template_parsing,
-                   options::OPT_fno_delayed_template_parsing,
-                   IsMSVCBefore2017Update3))
+                   options::OPT_fno_delayed_template_parsing, IsWindowsMSVC))
     CmdArgs.push_back("-fdelayed-template-parsing");
 
   // -fgnu-keywords default varies depending on language; only pass if