[WinCOFF] Add support for the .safeseh directive

.safeseh adds an entry to the .sxdata section to register all the
appropriate functions which may handle an exception.  This entry is not
a relocation to the symbol but instead the symbol table index of the
function.

llvm-svn: 238641

1 files changed, 27 insertions, 17 deletions

diff --git a/llvm/lib/MC/WinCOFFObjectWriter.cpp b/llvm/lib/MC/WinCOFFObjectWriter.cpp
index ddec16c..2f6d180 100644
--- a/llvm/lib/MC/WinCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/WinCOFFObjectWriter.cpp
@@ -21,6 +21,7 @@
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionCOFF.h"
@@ -76,6 +77,13 @@ public:
   void set_name_offset(uint32_t Offset);
 
   bool should_keep() const;
+
+  int64_t getIndex() const { return Index; }
+  void setIndex(int Value) {
+    Index = Value;
+    if (MC)
+      MC->setIndex(static_cast<uint32_t>(Value));
+  }
 };
 
 // This class contains staging data for a COFF relocation entry.
@@ -219,6 +227,10 @@ bool COFFSymbol::should_keep() const {
     return true;
   }
 
+  // if this is a safeseh handler, keep it
+  if (MC && (MC->getFlags() & COFF::SF_SafeSEH))
+    return true;
+
   // if the section its in is being droped, drop it
   if (Section->Number == -1)
     return false;
@@ -416,11 +428,13 @@ void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &Symbol,
     const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
     coff_symbol->Data.Value = getSymbolValue(Symbol, Layout);
 
-    coff_symbol->Data.Type = (Symbol.getFlags() & 0x0000FFFF) >> 0;
-    coff_symbol->Data.StorageClass = (Symbol.getFlags() & 0x00FF0000) >> 16;
+    coff_symbol->Data.Type =
+        (Symbol.getFlags() & COFF::SF_TypeMask) >> COFF::SF_TypeShift;
+    coff_symbol->Data.StorageClass =
+        (Symbol.getFlags() & COFF::SF_ClassMask) >> COFF::SF_ClassShift;
 
     // If no storage class was specified in the streamer, define it here.
-    if (coff_symbol->Data.StorageClass == 0) {
+    if (coff_symbol->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) {
       bool IsExternal = Symbol.isExternal() ||
                         (!Symbol.getFragment() && !Symbol.isVariable());
 
@@ -828,13 +842,9 @@ void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
 
   UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16;
 
-  DenseMap<COFFSection *, int32_t> SectionIndices(
-      NextPowerOf2(NumberOfSections));
-
   // Assign section numbers.
   size_t Number = 1;
   for (const auto &Section : Sections) {
-    SectionIndices[Section.get()] = Number;
     Section->Number = Number;
     Section->Symbol->Data.SectionNumber = Number;
     Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number;
@@ -877,12 +887,13 @@ void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
     if (Symbol->Section)
       Symbol->Data.SectionNumber = Symbol->Section->Number;
     if (Symbol->should_keep()) {
-      Symbol->Index = Header.NumberOfSymbols++;
+      Symbol->setIndex(Header.NumberOfSymbols++);
       // Update auxiliary symbol info.
       Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
       Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
-    } else
-      Symbol->Index = -1;
+    } else {
+      Symbol->setIndex(-1);
+    }
   }
 
   // Build string table.
@@ -904,11 +915,11 @@ void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
   // Fixup weak external references.
   for (auto &Symbol : Symbols) {
     if (Symbol->Other) {
-      assert(Symbol->Index != -1);
+      assert(Symbol->getIndex() != -1);
       assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
       assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
              "Symbol's aux symbol must be a Weak External!");
-      Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index;
+      Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex();
     }
   }
 
@@ -934,8 +945,7 @@ void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
     if (Assoc->Number == -1)
       continue;
 
-    Section->Symbol->Aux[0].Aux.SectionDefinition.Number =
-        SectionIndices[Assoc];
+    Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Assoc->Number;
   }
 
   // Assign file offsets to COFF object file structures.
@@ -984,8 +994,8 @@ void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
       offset += COFF::RelocationSize * Sec->Relocations.size();
 
       for (auto &Relocation : Sec->Relocations) {
-        assert(Relocation.Symb->Index != -1);
-        Relocation.Data.SymbolTableIndex = Relocation.Symb->Index;
+        assert(Relocation.Symb->getIndex() != -1);
+        Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
       }
     }
 
@@ -1067,7 +1077,7 @@ void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
          "Header::PointerToSymbolTable is insane!");
 
   for (auto &Symbol : Symbols)
-    if (Symbol->Index != -1)
+    if (Symbol->getIndex() != -1)
       WriteSymbol(*Symbol);
 
   OS.write(Strings.data().data(), Strings.data().size());