[WinEH] Create an llvm.x86.seh.exceptioninfo intrinsic

This intrinsic is like framerecover plus a load. It recovers the EH
registration stack allocation from the parent frame and loads the
exception information field out of it, giving back a pointer to an
EXCEPTION_POINTERS struct. It's designed for clang to use in SEH filter
expressions instead of accessing the EXCEPTION_POINTERS parameter that
is available on x64.

This required a minor change to MC to allow defining a label variable to
another absolute framerecover label variable.

llvm-svn: 239567

1 files changed, 4 insertions, 5 deletions

diff --git a/llvm/lib/MC/WinCOFFObjectWriter.cpp b/llvm/lib/MC/WinCOFFObjectWriter.cpp
index 423c7dc..56ef1c7 100644
--- a/llvm/lib/MC/WinCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/WinCOFFObjectWriter.cpp
@@ -526,13 +526,12 @@ bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol,
   if (!Symbol.isTemporary())
     return true;
 
-  // Absolute temporary labels are never visible.
-  if (!Symbol.isInSection())
+  // Temporary variable symbols are invisible.
+  if (Symbol.isVariable())
     return false;
 
-  // For now, all non-variable symbols are exported,
-  // the linker will sort the rest out for us.
-  return !Symbol.isVariable();
+  // Absolute temporary labels are never visible.
+  return !Symbol.isAbsolute();
 }
 
 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {