[MC] Accept a numeric value as an ELF section header's type

[atanasyan]

Summary

GAS supports specification of section header's type using a numeric value [1]. This patch brings the same functionality to LLVM. That allows to setup some target-specific section types belong to the SHT_LOPROC - SHT_HIPROC range. If we attempt to print unknown section type, MCSectionELF class shows an error message. It's better than print sole '@' sign without any section type name.

In case of MIPS, example of such section's type is SHT_MIPS_DWARF. Without the patch we will have to implement some workarounds in probably not-MIPS-specific part of code base to convert SHT_MIPS_DWARF to the @progbits while printing assembly and to assign SHT_MIPS_DWARF for @progbits sections named .debug_* if we encounter such section in an input assembly.

[1] https://sourceware.org/binutils/docs/as/Section.html

[atanasyan]

Ping?

[atanasyan]

Ping?

[atanasyan]

• Show an error if MCSectionELF attempt to print unknown section type value.
• Added a test case to check the error mentioned above.

llvm/trunk/lib/MC/MCParser/ELFAsmParser.cpp

bool ELFAsmParser::maybeParseSectionType(StringRef &TypeName) {
   if (L.isNot(AsmToken::Comma))
     return false;
   Lex();
   if (L.isNot(AsmToken::At) && L.isNot(AsmToken::Percent) &&
       L.isNot(AsmToken::String))
     return TokError("expected '@<type>', '%<type>' or \"<type>\"");
   if (!L.is(AsmToken::String))
     Lex();
-  if (getParser().parseIdentifier(TypeName))
+  if (L.is(AsmToken::Integer)) {
+    TypeName = getTok().getString();
+    Lex();
+  } else if (getParser().parseIdentifier(TypeName))
     return TokError("expected identifier in directive");
   return false;
 }
 
 bool ELFAsmParser::parseMergeSize(int64_t &Size) {
   if (getLexer().isNot(AsmToken::Comma))
     return TokError("expected the entry size");
   Lex();
if (TypeName.empty()) {
     else if (TypeName == "nobits")
       Type = ELF::SHT_NOBITS;
     else if (TypeName == "progbits")
       Type = ELF::SHT_PROGBITS;
     else if (TypeName == "note")
       Type = ELF::SHT_NOTE;
     else if (TypeName == "unwind")
       Type = ELF::SHT_X86_64_UNWIND;
-    else
+    else if (TypeName.getAsInteger(0, Type))
       return TokError("unknown section type");
   }
 
   if (UseLastGroup) {
     MCSectionSubPair CurrentSection = getStreamer().getCurrentSection();
     if (const MCSectionELF *Section =
             cast_or_null<MCSectionELF>(CurrentSection.first))
       if (const MCSymbol *Group = Section->getGroup()) {

llvm/trunk/lib/MC/MCSectionELF.cpp

 //===- lib/MC/MCSectionELF.cpp - ELF Code Section Representation ----------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/Triple.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/Support/ELF.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
 
 using namespace llvm;
 
 MCSectionELF::~MCSectionELF() = default; // anchor.
 
 // Decides whether a '.section' directive
void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
   else if (Type == ELF::SHT_NOBITS)
     OS << "nobits";
   else if (Type == ELF::SHT_NOTE)
     OS << "note";
   else if (Type == ELF::SHT_PROGBITS)
     OS << "progbits";
   else if (Type == ELF::SHT_X86_64_UNWIND)
     OS << "unwind";
+  else
+    report_fatal_error("unsupported type 0x" + Twine::utohexstr(Type) +
+                       " for section " + getSectionName());
 
   if (EntrySize) {
     assert(Flags & ELF::SHF_MERGE);
     OS << "," << EntrySize;
   }
 
   if (Flags & ELF::SHF_GROUP) {
     OS << ",";

llvm/trunk/test/MC/ELF/section-numeric-invalid-type.s

+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux-gnu %s -o - \
+// RUN:   | llvm-readobj -s -t | FileCheck --check-prefix=OBJ %s
+
+// RUN: not llvm-mc -filetype=asm -triple=x86_64-pc-linux-gnu %s -o - 2>&1 \
+// RUN:   | FileCheck --check-prefix=ASM %s
+
+  .section .sec,"a",@0x7fffffff
+
+// OBJ:      Section {
+// OBJ:        Name: .sec
+// OBJ-NEXT:   Type: (0x7FFFFFFF)
+// OBJ:      }
+
+// ASM: unsupported type 0x7fffffff for section .sec

llvm/trunk/test/MC/ELF/section-numeric-type.s

+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux-gnu %s -o - \
+// RUN:   | llvm-readobj -s -t | FileCheck --check-prefix=OBJ %s
+
+// RUN: llvm-mc -filetype=asm -triple=x86_64-pc-linux-gnu %s -o - \
+// RUN:   | FileCheck --check-prefix=ASM %s
+
+  .section .sec1,"a",@0x70000001
+  .section .sec2,"a",@1879048193
+
+// OBJ:      Section {
+// OBJ:        Name: .sec1
+// OBJ-NEXT:   Type: SHT_X86_64_UNWIND (0x70000001)
+// OBJ:      }
+// OBJ:      Section {
+// OBJ:        Name: .sec2
+// OBJ-NEXT:   Type: SHT_X86_64_UNWIND (0x70000001)
+// OBJ:      }
+
+// ASM: .section  .sec1,"a",@unwind
+// ASM: .section  .sec2,"a",@unwind