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, 41 insertions, 21 deletions

diff --git a/llvm/lib/MC/MCWinEH.cpp b/llvm/lib/MC/MCWinEH.cpp
index 8faf70737bf..f0c354feb61 100644
--- a/llvm/lib/MC/MCWinEH.cpp
+++ b/llvm/lib/MC/MCWinEH.cpp
@@ -17,27 +17,7 @@
 
 namespace llvm {
 namespace WinEH {
-const MCSection *UnwindEmitter::GetPDataSection(StringRef Suffix,
-                                                MCContext &Context) {
-  if (Suffix.empty())
-    return Context.getObjectFileInfo()->getPDataSection();
-  return Context.getCOFFSection((".pdata" + Suffix).str(),
-                                COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
-                                COFF::IMAGE_SCN_MEM_READ,
-                                SectionKind::getDataRel());
-}
-
-const MCSection *UnwindEmitter::GetXDataSection(StringRef Suffix,
-                                                MCContext &Context) {
-  if (Suffix.empty())
-    return Context.getObjectFileInfo()->getXDataSection();
-  return Context.getCOFFSection((".xdata" + Suffix).str(),
-                                COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
-                                COFF::IMAGE_SCN_MEM_READ,
-                                SectionKind::getDataRel());
-}
-
-StringRef UnwindEmitter::GetSectionSuffix(const MCSymbol *Function) {
+static StringRef getSectionSuffix(const MCSymbol *Function) {
   if (!Function || !Function->isInSection())
     return "";
 
@@ -59,6 +39,46 @@ StringRef UnwindEmitter::GetSectionSuffix(const MCSymbol *Function) {
 
   return "";
 }
+
+static const MCSection *getUnwindInfoSection(
+    StringRef SecName, const MCSectionCOFF *UnwindSec, const MCSymbol *Function,
+    MCContext &Context) {
+  // If Function is in a COMDAT, get or create an unwind info section in that
+  // COMDAT group.
+  if (Function && Function->isInSection()) {
+    const MCSectionCOFF *FunctionSection =
+        cast<MCSectionCOFF>(&Function->getSection());
+    if (FunctionSection->getCharacteristics() & COFF::IMAGE_SCN_LNK_COMDAT) {
+      return Context.getAssociativeCOFFSection(
+          UnwindSec, FunctionSection->getCOMDATSymbol());
+    }
+  }
+
+  // If Function is in a section other than .text, create a new .pdata section.
+  // Otherwise use the plain .pdata section.
+  StringRef Suffix = getSectionSuffix(Function);
+  if (Suffix.empty())
+    return UnwindSec;
+  return Context.getCOFFSection((SecName + Suffix).str(),
+                                COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
+                                COFF::IMAGE_SCN_MEM_READ,
+                                SectionKind::getDataRel());
+}
+
+const MCSection *UnwindEmitter::getPDataSection(const MCSymbol *Function,
+                                                MCContext &Context) {
+  const MCSectionCOFF *PData =
+      cast<MCSectionCOFF>(Context.getObjectFileInfo()->getPDataSection());
+  return getUnwindInfoSection(".pdata", PData, Function, Context);
+}
+
+const MCSection *UnwindEmitter::getXDataSection(const MCSymbol *Function,
+                                                MCContext &Context) {
+  const MCSectionCOFF *XData =
+      cast<MCSectionCOFF>(Context.getObjectFileInfo()->getXDataSection());
+  return getUnwindInfoSection(".xdata", XData, Function, Context);
+}
+
 }
 }