-fms-extensions: Implement half of #pragma init_seg

Summary:
This pragma is very rare.  We could *hypothetically* lower some uses of
it down to @llvm.global_ctors, but given that GlobalOpt isn't able to
optimize prioritized global ctors today, there's really no point.

If we wanted to do this in the future, I would check if the section used
in the pragma started with ".CRT$XC" and had up to two characters after
it.  Those two characters could form the 16-bit initialization priority
that we support in @llvm.global_ctors.  We would have to teach LLVM to
lower prioritized global ctors on COFF as well.

This should let us compile some silly uses of this pragma in WebKit /
Blink.

Reviewers: rsmith, majnemer

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4549

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213593 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/Sema/SemaAttr.cpp b/lib/Sema/SemaAttr.cpp
index 7c182a1c64..a7d606d545 100644
--- a/lib/Sema/SemaAttr.cpp
+++ b/lib/Sema/SemaAttr.cpp
@@ -431,6 +431,15 @@ void Sema::ActOnPragmaMSSection(SourceLocation PragmaLocation,
   UnifySection(SegmentName->getString(), SectionFlags, PragmaLocation);
 }
 
+void Sema::ActOnPragmaMSInitSeg(SourceLocation PragmaLocation,
+                                StringLiteral *SegmentName) {
+  // There's no stack to maintain, so we just have a current section.  When we
+  // see the default section, reset our current section back to null so we stop
+  // tacking on unnecessary attributes.
+  CurInitSeg = SegmentName->getString() == ".CRT$XCU" ? nullptr : SegmentName;
+  CurInitSegLoc = PragmaLocation;
+}
+
 void Sema::ActOnPragmaUnused(const Token &IdTok, Scope *curScope,
                              SourceLocation PragmaLoc) {