sets bit 0 of the function address of thumb function in .symtab

("T is 1 if the target symbol S has type STT_FUNC and the
symbol addresses a Thumb instruction ;it is 0 otherwise."
from "ELF for the ARM Architecture" 4.7.1.2)

Patch by Koan-Sin Tan!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131406 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCELFSymbolFlags.h

@@ -49,7 +49,8 @@ namespace llvm {
       ELF_STV_Hidden    = (ELF::STV_HIDDEN    << ELF_STV_Shift),
       ELF_STV_Protected = (ELF::STV_PROTECTED << ELF_STV_Shift),
 
-      ELF_Other_Weakref = (1                  << ELF_Other_Shift)
+      ELF_Other_Weakref = (1                  << ELF_Other_Shift),
+      ELF_Other_ThumbFunc = (2                << ELF_Other_Shift)
   };
 
 } // end namespace llvm

lib/MC/ELFObjectWriter.cpp

@@ -193,8 +193,13 @@ uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data,
   if (!Symbol.isInSection())
     return 0;
 
-  if (Data.getFragment())
+
+  if (Data.getFragment()) {
+    if (Data.getFlags() & ELF_Other_ThumbFunc)
+      return Layout.getSymbolOffset(&Data)+1;
+    else
       return Layout.getSymbolOffset(&Data);
+  }
 
   return 0;
 }

lib/MC/MCAsmStreamer.cpp

@@ -323,7 +323,8 @@ void MCAsmStreamer::EmitThumbFunc(MCSymbol *Func) {
   // This needs to emit to a temporary string to get properly quoted
   // MCSymbols when they have spaces in them.
   OS << "\t.thumb_func";
-  if (Func)
+  // Only Mach-O hasSubsectionsViaSymbols()
+  if (MAI.hasSubsectionsViaSymbols())
     OS << '\t' << *Func;
   EmitEOL();
 }

lib/MC/MCELF.cpp

@@ -57,13 +57,13 @@ void MCELF::SetVisibility(MCSymbolData &SD, unsigned Visibility) {
   assert(Visibility == ELF::STV_DEFAULT || Visibility == ELF::STV_INTERNAL ||
          Visibility == ELF::STV_HIDDEN || Visibility == ELF::STV_PROTECTED);
 
-  uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STV_Shift);
+  uint32_t OtherFlags = SD.getFlags() & ~(0x3 << ELF_STV_Shift);
   SD.setFlags(OtherFlags | (Visibility << ELF_STV_Shift));
 }
 
 unsigned MCELF::GetVisibility(MCSymbolData &SD) {
   unsigned Visibility =
-    (SD.getFlags() & (0xf << ELF_STV_Shift)) >> ELF_STV_Shift;
+    (SD.getFlags() & (0x3 << ELF_STV_Shift)) >> ELF_STV_Shift;
   assert(Visibility == ELF::STV_DEFAULT || Visibility == ELF::STV_INTERNAL ||
          Visibility == ELF::STV_HIDDEN || Visibility == ELF::STV_PROTECTED);
   return Visibility;

lib/MC/MCELFStreamer.cpp

@@ -66,6 +66,11 @@ void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
 
 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
   // FIXME: Anything needed here to flag the function as thumb?
+
+  getAssembler().setIsThumbFunc(Func);
+
+  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Func);
+  SD.setFlags(SD.getFlags() | ELF_Other_ThumbFunc);
 }
 
 void MCELFStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {

lib/Target/ARM/ARMAsmPrinter.cpp

@@ -274,7 +274,7 @@ void ARMAsmPrinter::EmitDwarfRegOp(const MachineLocation &MLoc) const {
 void ARMAsmPrinter::EmitFunctionEntryLabel() {
   if (AFI->isThumbFunction()) {
     OutStreamer.EmitAssemblerFlag(MCAF_Code16);
-    OutStreamer.EmitThumbFunc(Subtarget->isTargetDarwin()? CurrentFnSym : 0);
+    OutStreamer.EmitThumbFunc(CurrentFnSym);
   }
 
   OutStreamer.EmitLabel(CurrentFnSym);

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

@@ -15,6 +15,7 @@
 #include "llvm/MC/MCParser/MCAsmLexer.h"
 #include "llvm/MC/MCParser/MCAsmParser.h"
 #include "llvm/MC/MCParser/MCParsedAsmOperand.h"
+#include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCExpr.h"
@@ -2099,15 +2100,29 @@ bool ARMAsmParser::ParseDirectiveThumb(SMLoc L) {
 /// ParseDirectiveThumbFunc
 ///  ::= .thumbfunc symbol_name
 bool ARMAsmParser::ParseDirectiveThumbFunc(SMLoc L) {
+  const MCAsmInfo &MAI = getParser().getStreamer().getContext().getAsmInfo();
+  bool isMachO = MAI.hasSubsectionsViaSymbols();
+  StringRef Name;
+
+  // Darwin asm has function name after .thumb_func direction
+  // ELF doesn't
+  if (isMachO) {
     const AsmToken &Tok = Parser.getTok();
     if (Tok.isNot(AsmToken::Identifier) && Tok.isNot(AsmToken::String))
       return Error(L, "unexpected token in .thumb_func directive");
-  StringRef Name = Tok.getString();
+    Name = Tok.getString();
     Parser.Lex(); // Consume the identifier token.
+  }
+
   if (getLexer().isNot(AsmToken::EndOfStatement))
     return Error(L, "unexpected token in directive");
   Parser.Lex();
 
+  // FIXME: assuming function name will be the line following .thumb_func
+  if (!isMachO) {
+    Name = Parser.getTok().getString();
+  }
+
   // Mark symbol as a thumb symbol.
   MCSymbol *Func = getParser().getContext().GetOrCreateSymbol(Name);
   getParser().getStreamer().EmitThumbFunc(Func);

test/MC/ELF/elf-thumbfunc.s

@@ -0,0 +1,20 @@
+@@ test st_value bit 0 of thumb function
+@ RUN: llvm-mc %s -triple=thumbv7-linux-gnueabi -filetype=obj -o - | \
+@ RUN: elf-dump  | FileCheck %s
+	.syntax unified
+	.text
+	.globl	foo
+	.align	2
+	.type	foo,%function
+	.code	16
+	.thumb_func
+foo:
+	bx	lr
+
+@@ make sure foo is thumb function: bit 0 = 1 (st_value)
+@CHECK:           Symbol 0x00000004
+@CHECK-NEXT:      'st_name', 0x00000001
+@CHECK-NEXT:      'st_value', 0x00000001
+@CHECK-NEXT:      'st_size', 0x00000000
+@CHECK-NEXT:      'st_bind', 0x00000001
+@CHECK-NEXT:      'st_type', 0x00000002