MC Win64: Put unwind info for COMDAT code into the same COMDAT group

Summary:
This fixes a long standing issue where we would emit many little .text
sections and only one .pdata and .xdata section. Now we generate one
.pdata / .xdata pair per .text section and associate them correctly.

Fixes PR19667.

Reviewers: majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5181

llvm-svn: 217176

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index 7702da3540c..4266759b1f0 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -317,6 +317,22 @@ const MCSectionCOFF *MCContext::getCOFFSection(StringRef Section) {
   return Iter->second;
 }
 
+const MCSectionCOFF *
+MCContext::getAssociativeCOFFSection(const MCSectionCOFF *Sec,
+                                     const MCSymbol *KeySym) {
+  // Return the normal section if we don't have to be associative.
+  if (!KeySym)
+    return Sec;
+
+  // Make an associative section with the same name and kind as the normal
+  // section.
+  unsigned Characteristics =
+      Sec->getCharacteristics() | COFF::IMAGE_SCN_LNK_COMDAT;
+  return getCOFFSection(Sec->getSectionName(), Characteristics, Sec->getKind(),
+                        KeySym->getName(),
+                        COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
+}
+
 //===----------------------------------------------------------------------===//
 // Dwarf Management
 //===----------------------------------------------------------------------===//