MC: Add .section directive to COFF

Supports GAS flags "abdnrswxy". No support for alignment or subsections.

Fixes PR16366.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185669 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 172 insertions, 0 deletions

diff --git a/lib/MC/MCParser/COFFAsmParser.cpp b/lib/MC/MCParser/COFFAsmParser.cpp
index ad8f84c..c2a2261 100644
--- a/lib/MC/MCParser/COFFAsmParser.cpp
+++ b/lib/MC/MCParser/COFFAsmParser.cpp
@@ -35,6 +35,9 @@ class COFFAsmParser : public MCAsmParserExtension {
                           unsigned Characteristics,
                           SectionKind Kind);
 
+  bool ParseSectionName(StringRef &SectionName);
+  bool ParseSectionFlags(StringRef FlagsString, unsigned* Flags);
+
   virtual void Initialize(MCAsmParser &Parser) {
     // Call the base implementation.
     MCAsmParserExtension::Initialize(Parser);
@@ -42,6 +45,7 @@ class COFFAsmParser : public MCAsmParserExtension {
     addDirectiveHandler<&COFFAsmParser::ParseSectionDirectiveText>(".text");
     addDirectiveHandler<&COFFAsmParser::ParseSectionDirectiveData>(".data");
     addDirectiveHandler<&COFFAsmParser::ParseSectionDirectiveBSS>(".bss");
+    addDirectiveHandler<&COFFAsmParser::ParseDirectiveSection>(".section");
     addDirectiveHandler<&COFFAsmParser::ParseDirectiveDef>(".def");
     addDirectiveHandler<&COFFAsmParser::ParseDirectiveScl>(".scl");
     addDirectiveHandler<&COFFAsmParser::ParseDirectiveType>(".type");
@@ -100,6 +104,7 @@ class COFFAsmParser : public MCAsmParserExtension {
                               SectionKind::getBSS());
   }
 
+  bool ParseDirectiveSection(StringRef, SMLoc);
   bool ParseDirectiveDef(StringRef, SMLoc);
   bool ParseDirectiveScl(StringRef, SMLoc);
   bool ParseDirectiveType(StringRef, SMLoc);
@@ -130,6 +135,119 @@ public:
 
 } // end annonomous namespace.
 
+static SectionKind computeSectionKind(unsigned Flags) {
+  if (Flags & COFF::IMAGE_SCN_MEM_EXECUTE)
+    return SectionKind::getText();
+  if (Flags & COFF::IMAGE_SCN_MEM_READ &&
+      (Flags & COFF::IMAGE_SCN_MEM_WRITE) == 0)
+    return SectionKind::getReadOnly();
+  return SectionKind::getDataRel();
+}
+
+bool COFFAsmParser::ParseSectionFlags(StringRef FlagsString, unsigned* Flags) {
+  enum {
+    None      = 0,
+    Alloc     = 1 << 0,
+    Code      = 1 << 1,
+    Load      = 1 << 2,
+    InitData  = 1 << 3,
+    Shared    = 1 << 4,
+    NoLoad    = 1 << 5,
+    NoRead    = 1 << 6,
+    NoWrite  =  1 << 7
+  };
+
+  bool ReadOnlyRemoved = false;
+  unsigned SecFlags = None;
+
+  for (unsigned i = 0; i < FlagsString.size(); ++i) {
+    switch (FlagsString[i]) {
+    case 'a':
+      // Ignored.
+      break;
+
+    case 'b': // bss section
+      SecFlags |= Alloc;
+      if (SecFlags & InitData)
+        return TokError("conflicting section flags 'b' and 'd'.");
+      SecFlags &= ~Load;
+      break;
+
+    case 'd': // data section
+      SecFlags |= InitData;
+      if (SecFlags & Alloc)
+        return TokError("conflicting section flags 'b' and 'd'.");
+      SecFlags &= ~NoWrite;
+      if ((SecFlags & NoLoad) == 0)
+        SecFlags |= Load;
+      break;
+
+    case 'n': // section is not loaded
+      SecFlags |= NoLoad;
+      SecFlags &= ~Load;
+      break;
+
+    case 'r': // read-only
+      ReadOnlyRemoved = false;
+      SecFlags |= NoWrite;
+      if ((SecFlags & Code) == 0)
+        SecFlags |= InitData;
+      if ((SecFlags & NoLoad) == 0)
+        SecFlags |= Load;
+      break;
+
+    case 's': // shared section
+      SecFlags |= Shared | InitData;
+      SecFlags &= ~NoWrite;
+      if ((SecFlags & NoLoad) == 0)
+        SecFlags |= Load;
+      break;
+
+    case 'w': // writable
+      SecFlags &= ~NoWrite;
+      ReadOnlyRemoved = true;
+      break;
+
+    case 'x': // executable section
+      SecFlags |= Code;
+      if ((SecFlags & NoLoad) == 0)
+        SecFlags |= Load;
+      if (!ReadOnlyRemoved)
+        SecFlags |= NoWrite;
+      break;
+
+    case 'y': // not readable
+      SecFlags |= NoRead | NoWrite;
+      break;
+
+    default:
+      return TokError("unknown flag");
+    }
+  }
+
+  *Flags = 0;
+
+  if (SecFlags == None)
+    SecFlags = InitData;
+
+  if (SecFlags & Code)
+    *Flags |= COFF::IMAGE_SCN_CNT_CODE | COFF::IMAGE_SCN_MEM_EXECUTE;
+  if (SecFlags & InitData)
+    *Flags |= COFF::IMAGE_SCN_CNT_INITIALIZED_DATA;
+  if ((SecFlags & Alloc) && (SecFlags & Load) == 0)
+    *Flags |= COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA;
+  if (SecFlags & NoLoad)
+    *Flags |= COFF::IMAGE_SCN_LNK_REMOVE;
+  if ((SecFlags & NoRead) == 0)
+    *Flags |= COFF::IMAGE_SCN_MEM_READ;
+  if ((SecFlags & NoWrite) == 0)
+    *Flags |= COFF::IMAGE_SCN_MEM_WRITE;
+  if (SecFlags & Shared)
+    *Flags |= COFF::IMAGE_SCN_MEM_SHARED;
+
+  return false;
+}
+
 /// ParseDirectiveSymbolAttribute
 ///  ::= { ".weak", ... } [ identifier ( , identifier )* ]
 bool COFFAsmParser::ParseDirectiveSymbolAttribute(StringRef Directive, SMLoc) {
@@ -174,6 +292,60 @@ bool COFFAsmParser::ParseSectionSwitch(StringRef Section,
   return false;
 }
 
+bool COFFAsmParser::ParseSectionName(StringRef &SectionName) {
+  if (!getLexer().is(AsmToken::Identifier))
+    return true;
+
+  SectionName = getTok().getIdentifier();
+  Lex();
+  return false;
+}
+
+// .section name [, "flags"]
+//
+// Supported flags:
+//   a: Ignored.
+//   b: BSS section (uninitialized data)
+//   d: data section (initialized data)
+//   n: Discardable section
+//   r: Readable section
+//   s: Shared section
+//   w: Writable section
+//   x: Executable section
+//   y: Not-readable section (clears 'r')
+//
+// Subsections are not supported.
+bool COFFAsmParser::ParseDirectiveSection(StringRef, SMLoc) {
+  StringRef SectionName;
+
+  if (ParseSectionName(SectionName))
+    return TokError("expected identifier in directive");
+
+  unsigned Flags = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
+                   COFF::IMAGE_SCN_MEM_READ |
+                   COFF::IMAGE_SCN_MEM_WRITE;
+
+  if (getLexer().is(AsmToken::Comma)) {
+    Lex();
+
+    if (getLexer().isNot(AsmToken::String))
+      return TokError("expected string in directive");
+
+    StringRef FlagsStr = getTok().getStringContents();
+    Lex();
+
+    if (ParseSectionFlags(FlagsStr, &Flags))
+      return true;
+  }
+
+  if (getLexer().isNot(AsmToken::EndOfStatement))
+    return TokError("unexpected token in directive");
+
+  SectionKind Kind = computeSectionKind(Flags);
+  ParseSectionSwitch(SectionName, Flags, Kind);
+  return false;
+}
+
 bool COFFAsmParser::ParseDirectiveDef(StringRef, SMLoc) {
   StringRef SymbolName;