Added Mapping Symbols for ARM ELF

Before this patch, when you objdump an LLVM-compiled file, objdump tried to
decode data-in-code sections as if they were code.  This patch adds the missing
Mapping Symbols, as defined by "ELF for the ARM Architecture" (ARM IHI 0044D).

Patch based on work by Greg Fitzgerald.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169609 91177308-0d34-0410-b5e6-96231b3b80d8

19 files changed, 515 insertions, 39 deletions

diff --git a/lib/MC/MCELF.h b/include/llvm/MC/MCELF.h
index e08f1e6..e08f1e6 100644
--- a/lib/MC/MCELF.h
+++ b/include/llvm/MC/MCELF.h
diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp
index 5b10fbb..b0623d3 100644
--- a/lib/MC/ELFObjectWriter.cpp
+++ b/lib/MC/ELFObjectWriter.cpp
@@ -12,7 +12,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCELFObjectWriter.h"
-#include "MCELF.h"
 #include "llvm/ADT/OwningPtr.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
@@ -22,6 +21,7 @@
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCELF.h"
 #include "llvm/MC/MCELFSymbolFlags.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCFixupKindInfo.h"
diff --git a/lib/MC/MCELF.cpp b/lib/MC/MCELF.cpp
index f9f98e0..4db2846 100644
--- a/lib/MC/MCELF.cpp
+++ b/lib/MC/MCELF.cpp
@@ -11,7 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "MCELF.h"
+#include "llvm/MC/MCELF.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCELFSymbolFlags.h"
 #include "llvm/MC/MCFixupKindInfo.h"
diff --git a/lib/MC/MCELFStreamer.cpp b/lib/MC/MCELFStreamer.cpp
index a3178ff..c58a6ae 100644
--- a/lib/MC/MCELFStreamer.cpp
+++ b/lib/MC/MCELFStreamer.cpp
@@ -12,15 +12,11 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCELFStreamer.h"
-
-#include "MCELF.h"
 #include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/StringExtras.h"
-#include "llvm/ADT/Twine.h"
-#include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCCodeEmitter.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCELF.h"
 #include "llvm/MC/MCELFSymbolFlags.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
@@ -104,15 +100,6 @@ void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
   llvm_unreachable("invalid assembler 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) {
   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
   // MCObjectStreamer.
@@ -396,9 +383,7 @@ void MCELFStreamer::FinishImpl() {
 
   this->MCObjectStreamer::FinishImpl();
 }
-
-void MCELFStreamer::EmitTCEntry(const MCSymbol &S)
-{
+void MCELFStreamer::EmitTCEntry(const MCSymbol &S) {
   // Creates a R_PPC64_TOC relocation
   MCObjectStreamer::EmitSymbolValue(&S, 8, 0);
 }
@@ -414,6 +399,10 @@ MCStreamer *llvm::createELFStreamer(MCContext &Context, MCAsmBackend &MAB,
   return S;
 }
 
+void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
+  llvm_unreachable("Generic ELF doesn't support this directive");
+}
+
 void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
   llvm_unreachable("ELF doesn't support this directive");
 }
diff --git a/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp b/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
new file mode 100644
index 0000000..10891a4
--- /dev/null
+++ b/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
@@ -0,0 +1,201 @@
+//===- lib/MC/ARMELFStreamer.cpp - ELF Object Output for ARM --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file assembles .s files and emits ARM ELF .o object files. Different
+// from generic ELF streamer in emitting mapping symbols ($a, $t and $d) to
+// delimit regions of data and code.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCELFStreamer.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/MC/MCAssembler.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCELF.h"
+#include "llvm/MC/MCELFStreamer.h"
+#include "llvm/MC/MCELFSymbolFlags.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCObjectStreamer.h"
+#include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCValue.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ELF.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+namespace {
+
+/// Extend the generic ELFStreamer class so that it can emit mapping symbols at
+/// the appropriate points in the object files. These symbols are defined in the
+/// ARM ELF ABI: infocenter.arm.com/help/topic/com.arm.../IHI0044D_aaelf.pdf.
+///
+/// In brief: $a, $t or $d should be emitted at the start of each contiguous
+/// region of ARM code, Thumb code or data in a section. In practice, this
+/// emission does not rely on explicit assembler directives but on inherent
+/// properties of the directives doing the emission (e.g. ".byte" is data, "add
+/// r0, r0, r0" an instruction).
+///
+/// As a result this system is orthogonal to the DataRegion infrastructure used
+/// by MachO. Beware!
+class ARMELFStreamer : public MCELFStreamer {
+public:
+  ARMELFStreamer(MCContext &Context, MCAsmBackend &TAB,
+                 raw_ostream &OS, MCCodeEmitter *Emitter, bool IsThumb)
+    : MCELFStreamer(Context, TAB, OS, Emitter),
+      IsThumb(IsThumb), MappingSymbolCounter(0), LastEMS(EMS_None) {
+  }
+
+  ~ARMELFStreamer() {}
+
+  virtual void ChangeSection(const MCSection *Section) {
+    // We have to keep track of the mapping symbol state of any sections we
+    // use. Each one should start off as EMS_None, which is provided as the
+    // default constructor by DenseMap::lookup.
+    LastMappingSymbols[getPreviousSection()] = LastEMS;
+    LastEMS = LastMappingSymbols.lookup(Section);
+
+    MCELFStreamer::ChangeSection(Section);
+  }
+
+  /// This function is the one used to emit instruction data into the ELF
+  /// streamer. We override it to add the appropriate mapping symbol if
+  /// necessary.
+  virtual void EmitInstruction(const MCInst& Inst) {
+    if (IsThumb)
+      EmitThumbMappingSymbol();
+    else
+      EmitARMMappingSymbol();
+
+    MCELFStreamer::EmitInstruction(Inst);
+  }
+
+  /// This is one of the functions used to emit data into an ELF section, so the
+  /// ARM streamer overrides it to add the appropriate mapping symbol ($d) if
+  /// necessary.
+  virtual void EmitBytes(StringRef Data, unsigned AddrSpace) {
+    EmitDataMappingSymbol();
+    MCELFStreamer::EmitBytes(Data, AddrSpace);
+  }
+
+  /// This is one of the functions used to emit data into an ELF section, so the
+  /// ARM streamer overrides it to add the appropriate mapping symbol ($d) if
+  /// necessary.
+  virtual void EmitValueImpl(const MCExpr *Value, unsigned Size,
+                             unsigned AddrSpace) {
+    EmitDataMappingSymbol();
+    MCELFStreamer::EmitValueImpl(Value, Size, AddrSpace);
+  }
+
+  virtual void EmitAssemblerFlag(MCAssemblerFlag Flag) {
+    MCELFStreamer::EmitAssemblerFlag(Flag);
+
+    switch (Flag) {
+    case MCAF_SyntaxUnified:
+      return; // no-op here.
+    case MCAF_Code16:
+      IsThumb = true;
+      return; // Change to Thumb mode
+    case MCAF_Code32:
+      IsThumb = false;
+      return; // Change to ARM mode
+    case MCAF_Code64:
+      return;
+    case MCAF_SubsectionsViaSymbols:
+      return;
+    }
+  }
+
+private:
+  enum ElfMappingSymbol {
+    EMS_None,
+    EMS_ARM,
+    EMS_Thumb,
+    EMS_Data
+  };
+
+  void EmitDataMappingSymbol() {
+    if (LastEMS == EMS_Data) return;
+    EmitMappingSymbol("$d");
+    LastEMS = EMS_Data;
+  }
+
+  void EmitThumbMappingSymbol() {
+    if (LastEMS == EMS_Thumb) return;
+    EmitMappingSymbol("$t");
+    LastEMS = EMS_Thumb;
+  }
+
+  void EmitARMMappingSymbol() {
+    if (LastEMS == EMS_ARM) return;
+    EmitMappingSymbol("$a");
+    LastEMS = EMS_ARM;
+  }
+
+  void EmitMappingSymbol(StringRef Name) {
+    MCSymbol *Start = getContext().CreateTempSymbol();
+    EmitLabel(Start);
+
+    StringRef UniqueName = Name.str() + "." + itostr(MappingSymbolCounter++);
+    MCSymbol *Symbol = getContext().GetOrCreateSymbol(UniqueName);
+
+    MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
+    MCELF::SetType(SD, ELF::STT_NOTYPE);
+    MCELF::SetBinding(SD, ELF::STB_LOCAL);
+    SD.setExternal(false);
+    Symbol->setSection(*getCurrentSection());
+
+    const MCExpr *Value = MCSymbolRefExpr::Create(Start, getContext());
+    Symbol->setVariableValue(Value);
+  }
+
+  void 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);
+  }
+
+
+  bool IsThumb;
+  int64_t MappingSymbolCounter;
+
+  DenseMap<const MCSection *, ElfMappingSymbol> LastMappingSymbols;
+  ElfMappingSymbol LastEMS;
+
+  /// @}
+};
+}
+
+namespace llvm {
+  MCELFStreamer* createARMELFStreamer(MCContext &Context, MCAsmBackend &TAB,
+                                      raw_ostream &OS, MCCodeEmitter *Emitter,
+                                      bool RelaxAll, bool NoExecStack,
+                                      bool IsThumb) {
+    ARMELFStreamer *S = new ARMELFStreamer(Context, TAB, OS, Emitter, IsThumb);
+    if (RelaxAll)
+      S->getAssembler().setRelaxAll(true);
+    if (NoExecStack)
+      S->getAssembler().setNoExecStack(true);
+    return S;
+  }
+
+}
+
+
diff --git a/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.h b/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.h
new file mode 100644
index 0000000..77ae5d2
--- /dev/null
+++ b/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.h
@@ -0,0 +1,27 @@
+//===-- ARMELFStreamer.h - ELF Streamer for ARM ------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements ELF streamer information for the ARM backend.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef ARM_ELF_STREAMER_H
+#define ARM_ELF_STREAMER_H
+
+#include "llvm/MC/MCELFStreamer.h"
+
+namespace llvm {
+
+  MCELFStreamer* createARMELFStreamer(MCContext &Context, MCAsmBackend &TAB,
+                                      raw_ostream &OS, MCCodeEmitter *Emitter,
+                                      bool RelaxAll, bool NoExecStack,
+                                      bool IsThumb);
+}
+
+#endif // ARM_ELF_STREAMER_H
diff --git a/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp b/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
index 4dfd69b..c4dacfe 100644
--- a/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
+++ b/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
@@ -12,6 +12,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "ARMMCTargetDesc.h"
+#include "ARMELFStreamer.h"
+#include "ARMMCAsmInfo.h"
 #include "ARMBaseInfo.h"
 #include "ARMMCAsmInfo.h"
 #include "InstPrinter/ARMInstPrinter.h"
@@ -186,7 +188,8 @@ static MCStreamer *createMCStreamer(const Target &T, StringRef TT,
     llvm_unreachable("ARM does not support Windows COFF format");
   }
 
-  return createELFStreamer(Ctx, MAB, OS, Emitter, false, NoExecStack);
+  return createARMELFStreamer(Ctx, MAB, OS, Emitter, false, NoExecStack,
+                              TheTriple.getArch() == Triple::thumb);
 }
 
 static MCInstPrinter *createARMMCInstPrinter(const Target &T,
diff --git a/lib/Target/ARM/MCTargetDesc/CMakeLists.txt b/lib/Target/ARM/MCTargetDesc/CMakeLists.txt
index 2565994..e17eb4d 100644
--- a/lib/Target/ARM/MCTargetDesc/CMakeLists.txt
+++ b/lib/Target/ARM/MCTargetDesc/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_llvm_library(LLVMARMDesc
   ARMAsmBackend.cpp
   ARMELFObjectWriter.cpp
+  ARMELFStreamer.cpp
   ARMMCAsmInfo.cpp
   ARMMCCodeEmitter.cpp
   ARMMCExpr.cpp
diff --git a/test/CodeGen/ARM/2010-11-30-reloc-movt.ll b/test/CodeGen/ARM/2010-11-30-reloc-movt.ll
index 8b164c5..94a0541 100644
--- a/test/CodeGen/ARM/2010-11-30-reloc-movt.ll
+++ b/test/CodeGen/ARM/2010-11-30-reloc-movt.ll
@@ -23,7 +23,7 @@ entry:
 
 ; OBJ:            Relocation 0
 ; OBJ-NEXT:       'r_offset', 0x00000004
-; OBJ-NEXT:       'r_sym', 0x000007
+; OBJ-NEXT:       'r_sym', 0x000009
 ; OBJ-NEXT:        'r_type', 0x2b
 
 ; OBJ:          Relocation 1
@@ -33,7 +33,7 @@ entry:
 
 ; OBJ:          # Relocation 2
 ; OBJ-NEXT:       'r_offset', 0x0000000c
-; OBJ-NEXT:       'r_sym', 0x000008
+; OBJ-NEXT:       'r_sym', 0x00000a
 ; OBJ-NEXT:       'r_type', 0x1c
 
 }
diff --git a/test/MC/ARM/data-in-code.ll b/test/MC/ARM/data-in-code.ll
new file mode 100644
index 0000000..c2feec5
--- /dev/null
+++ b/test/MC/ARM/data-in-code.ll
@@ -0,0 +1,176 @@
+;; RUN: llc -O0 -mtriple=armv7-linux-gnueabi -filetype=obj %s -o - | \
+;; RUN:   elf-dump | FileCheck -check-prefix=ARM %s
+
+;; RUN: llc -O0 -mtriple=thumbv7-linux-gnueabi -filetype=obj %s -o - | \
+;; RUN:   elf-dump --dump-section-data | FileCheck -check-prefix=TMB %s
+
+;; Ensure that if a jump table is generated that it has Mapping Symbols
+;; marking the data-in-code region.
+
+define void @foo(i32* %ptr) nounwind ssp {
+  %tmp = load i32* %ptr, align 4
+  switch i32 %tmp, label %default [
+    i32 11, label %bb0
+    i32 10, label %bb1
+    i32 8, label %bb2
+    i32 4, label %bb3
+    i32 2, label %bb4
+    i32 6, label %bb5
+    i32 9, label %bb6
+    i32 15, label %bb7
+    i32 1, label %bb8
+    i32 3, label %bb9
+    i32 5, label %bb10
+    i32 30, label %bb11
+    i32 31, label %bb12
+    i32 13, label %bb13
+    i32 14, label %bb14
+    i32 20, label %bb15
+    i32 19, label %bb16
+    i32 17, label %bb17
+    i32 18, label %bb18
+    i32 21, label %bb19
+    i32 22, label %bb20
+    i32 16, label %bb21
+    i32 24, label %bb22
+    i32 25, label %bb23
+    i32 26, label %bb24
+    i32 27, label %bb25
+    i32 28, label %bb26
+    i32 23, label %bb27
+    i32 12, label %bb28
+  ]
+
+default:
+  br label %exit
+bb0:
+  br label %exit
+bb1:
+  br label %exit
+bb2:
+  br label %exit
+bb3:
+  br label %exit
+bb4:
+  br label %exit
+bb5:
+  br label %exit
+bb6:
+  br label %exit
+bb7:
+  br label %exit
+bb8:
+  br label %exit
+bb9:
+  br label %exit
+bb10:
+  br label %exit
+bb11:
+  br label %exit
+bb12:
+  br label %exit
+bb13:
+  br label %exit
+bb14:
+  br label %exit
+bb15:
+  br label %exit
+bb16:
+  br label %exit
+bb17:
+  br label %exit
+bb18:
+  br label %exit
+bb19:
+  br label %exit
+bb20:
+  br label %exit
+bb21:
+  br label %exit
+bb22:
+  br label %exit
+bb23:
+  br label %exit
+bb24:
+  br label %exit
+bb25:
+  br label %exit
+bb26:
+  br label %exit
+bb27:
+  br label %exit
+bb28:
+  br label %exit
+
+
+exit:
+
+  ret void
+}
+
+;; ARM:         # Symbol 2
+;; ARM-NEXT:    $a
+;; ARM-NEXT:   'st_value', 0x00000000
+;; ARM-NEXT:   'st_size', 0x00000000
+;; ARM-NEXT:   'st_bind', 0x0
+;; ARM-NEXT:   'st_type', 0x0
+;; ARM-NEXT:   'st_other'
+;; ARM-NEXT:   'st_shndx', [[MIXED_SECT:0x[0-9a-f]+]]
+
+;; ARM:         # Symbol 3
+;; ARM-NEXT:    $a
+;; ARM-NEXT:   'st_value', 0x000000ac
+;; ARM-NEXT:   'st_size', 0x00000000
+;; ARM-NEXT:   'st_bind', 0x0
+;; ARM-NEXT:   'st_type', 0x0
+;; ARM-NEXT:   'st_other'
+;; ARM-NEXT:   'st_shndx', [[MIXED_SECT]]
+
+;; ARM:         # Symbol 4
+;; ARM-NEXT:    $d
+;; ARM-NEXT:    'st_value', 0x00000000
+;; ARM-NEXT:    'st_size', 0x00000000
+;; ARM-NEXT:    'st_bind', 0x0
+;; ARM-NEXT:    'st_type', 0x0
+
+;; ARM:         # Symbol 5
+;; ARM-NEXT:    $d
+;; ARM-NEXT:   'st_value', 0x00000030
+;; ARM-NEXT:   'st_size', 0x00000000
+;; ARM-NEXT:   'st_bind', 0x0
+;; ARM-NEXT:   'st_type', 0x0
+;; ARM-NEXT:   'st_other'
+;; ARM-NEXT:   'st_shndx', [[MIXED_SECT]]
+
+;; ARM-NOT:     ${{[atd]}}
+
+;; TMB:         # Symbol 3
+;; TMB-NEXT:    $d
+;; TMB-NEXT:   'st_value', 0x00000016
+;; TMB-NEXT:   'st_size', 0x00000000
+;; TMB-NEXT:   'st_bind', 0x0
+;; TMB-NEXT:   'st_type', 0x0
+;; TMB-NEXT:   'st_other'
+;; TMB-NEXT:   'st_shndx', [[MIXED_SECT:0x[0-9a-f]+]]
+
+;; TMB:         # Symbol 4
+;; TMB-NEXT:    $t
+;; TMB-NEXT:   'st_value', 0x00000000
+;; TMB-NEXT:   'st_size', 0x00000000
+;; TMB-NEXT:   'st_bind', 0x0
+;; TMB-NEXT:   'st_type', 0x0
+;; TMB-NEXT:   'st_other'
+;; TMB-NEXT:   'st_shndx', [[MIXED_SECT]]
+
+;; TMB:         # Symbol 5
+;; TMB-NEXT:    $t
+;; TMB-NEXT:   'st_value', 0x00000036
+;; TMB-NEXT:   'st_size', 0x00000000
+;; TMB-NEXT:   'st_bind', 0x0
+;; TMB-NEXT:   'st_type', 0x0
+;; TMB-NEXT:   'st_other'
+;; TMB-NEXT:   'st_shndx', [[MIXED_SECT]]
+
+
+;; TMB-NOT:     ${{[atd]}}
+
diff --git a/test/MC/ARM/elf-reloc-01.ll b/test/MC/ARM/elf-reloc-01.ll
index c98026b..3ebd7c6 100644
--- a/test/MC/ARM/elf-reloc-01.ll
+++ b/test/MC/ARM/elf-reloc-01.ll
@@ -62,9 +62,9 @@ declare void @exit(i32) noreturn nounwind
 
 ;; OBJ:          Relocation 1
 ;; OBJ-NEXT:     'r_offset',
-;; OBJ-NEXT:     'r_sym', 0x000002
+;; OBJ-NEXT:     'r_sym', 0x000007
 ;; OBJ-NEXT:     'r_type', 0x2b
 
-;; OBJ:         Symbol 2
+;; OBJ:         Symbol 7
 ;; OBJ-NEXT:    '_MergedGlobals'
 ;; OBJ-NEXT:    'st_value', 0x00000010
diff --git a/test/MC/ARM/elf-reloc-02.ll b/test/MC/ARM/elf-reloc-02.ll
index e51bac3..6b6b03c 100644
--- a/test/MC/ARM/elf-reloc-02.ll
+++ b/test/MC/ARM/elf-reloc-02.ll
@@ -42,9 +42,9 @@ declare i32 @write(...)
 declare void @exit(i32) noreturn nounwind
 
 ;; OBJ:        Relocation 0
-;; OBJ-NEXT:    'r_offset', 
-;; OBJ-NEXT:    'r_sym', 0x000002
+;; OBJ-NEXT:    'r_offset',
+;; OBJ-NEXT:    'r_sym', 0x000005
 ;; OBJ-NEXT:    'r_type', 0x2b
 
-;; OBJ:          Symbol 2
+;; OBJ:          Symbol 5
 ;; OBJ-NEXT:    '.L.str'
diff --git a/test/MC/ARM/elf-reloc-03.ll b/test/MC/ARM/elf-reloc-03.ll
index 922242f..87f91c1 100644
--- a/test/MC/ARM/elf-reloc-03.ll
+++ b/test/MC/ARM/elf-reloc-03.ll
@@ -89,9 +89,9 @@ entry:
 declare void @exit(i32) noreturn nounwind
 
 ;; OBJ:           Relocation 1
-;; OBJ-NEXT:     'r_offset', 
-;; OBJ-NEXT:     'r_sym', 0x00000c
+;; OBJ-NEXT:     'r_offset',
+;; OBJ-NEXT:     'r_sym', 0x000010
 ;; OBJ-NEXT:     'r_type', 0x2b
 
-;; OBJ:      Symbol 12
+;; OBJ:      Symbol 16
 ;; OBJ-NEXT:    'vtable'
diff --git a/test/MC/ARM/elf-reloc-condcall.s b/test/MC/ARM/elf-reloc-condcall.s
index 08b4ecc..3fafb43 100644
--- a/test/MC/ARM/elf-reloc-condcall.s
+++ b/test/MC/ARM/elf-reloc-condcall.s
@@ -9,25 +9,25 @@
 // OBJ: .rel.text
 
 // OBJ: 'r_offset', 0x00000000
-// OBJ-NEXT:  'r_sym', 0x000004
+// OBJ-NEXT:  'r_sym', 0x000005
 // OBJ-NEXT: 'r_type', 0x1d
 
 // OBJ: 'r_offset', 0x00000004
-// OBJ-NEXT:  'r_sym', 0x000004
+// OBJ-NEXT:  'r_sym', 0x000005
 // OBJ-NEXT: 'r_type', 0x1c
 
 // OBJ: 'r_offset', 0x00000008
-// OBJ-NEXT:  'r_sym', 0x000004
+// OBJ-NEXT:  'r_sym', 0x000005
 // OBJ-NEXT: 'r_type', 0x1c
 
 // OBJ: 'r_offset', 0x0000000c
-// OBJ-NEXT:  'r_sym', 0x000004
+// OBJ-NEXT:  'r_sym', 0x000005
 // OBJ-NEXT: 'r_type', 0x1d
 
 // OBJ: 'r_offset', 0x00000010
-// OBJ-NEXT:  'r_sym', 0x000004
+// OBJ-NEXT:  'r_sym', 0x000005
 // OBJ-NEXT: 'r_type', 0x1d
 
 // OBJ: .symtab
-// OBJ: Symbol 4
+// OBJ: Symbol 5
 // OBJ-NEXT: some_label
diff --git a/test/MC/ARM/elf-thumbfunc-reloc.ll b/test/MC/ARM/elf-thumbfunc-reloc.ll
index ecac11d..b2f253d 100644
--- a/test/MC/ARM/elf-thumbfunc-reloc.ll
+++ b/test/MC/ARM/elf-thumbfunc-reloc.ll
@@ -28,10 +28,10 @@ entry:
 ; 00000008  0000070a R_ARM_THM_CALL    00000001   foo
 ; CHECK:           Relocation 0
 ; CHECK-NEXT:      'r_offset', 0x00000008
-; CHECK-NEXT:      'r_sym', 0x000007
+; CHECK-NEXT:      'r_sym', 0x000009
 ; CHECK-NEXT:      'r_type', 0x0a
 
 ; make sure foo is thumb function: bit 0 = 1
-; CHECK:           Symbol 7
+; CHECK:           Symbol 9
 ; CHECK-NEXT:      'foo'
 ; CHECK-NEXT:      'st_value', 0x00000001
diff --git a/test/MC/ARM/elf-thumbfunc.s b/test/MC/ARM/elf-thumbfunc.s
index 0aa7f41..91b2eee 100644
--- a/test/MC/ARM/elf-thumbfunc.s
+++ b/test/MC/ARM/elf-thumbfunc.s
@@ -12,7 +12,7 @@ foo:
 	bx	lr
 
 @@ make sure foo is thumb function: bit 0 = 1 (st_value)
-@CHECK:           Symbol 4
+@CHECK:           Symbol 5
 @CHECK-NEXT:      'st_name', 0x00000001
 @CHECK-NEXT:      'st_value', 0x00000001
 @CHECK-NEXT:      'st_size', 0x00000000
diff --git a/test/MC/ARM/mapping-within-section.s b/test/MC/ARM/mapping-within-section.s
new file mode 100644
index 0000000..56dd6ef
--- /dev/null
+++ b/test/MC/ARM/mapping-within-section.s
@@ -0,0 +1,33 @@
+@ RUN: llvm-mc -triple=arm-linux-gnueabi -filetype=obj < %s | llvm-objdump -t - | FileCheck %s
+
+    .text
+@ $a at 0x0000
+    add r0, r0, r0
+@ $d at 0x0004
+    .word 42
+    .thumb
+@ $t at 0x0008
+    adds r0, r0, r0
+    adds r0, r0, r0
+@ $a at 0x000c
+    .arm
+    add r0, r0, r0
+@ $t at 0x0010
+    .thumb
+    adds r0, r0, r0
+@ $d at 0x0012
+    .ascii "012"
+    .byte 1
+    .byte 2
+    .byte 3
+@ $a at 0x0018
+    .arm
+    add r0, r0, r0
+
+@ CHECK:      00000000         .text  00000000 $a
+@ CHECK-NEXT: 0000000c         .text  00000000 $a
+@ CHECK-NEXT: 00000018         .text  00000000 $a
+@ CHECK-NEXT: 00000004         .text  00000000 $d
+@ CHECK-NEXT: 00000012         .text  00000000 $d
+@ CHECK-NEXT: 00000008         .text  00000000 $t
+@ CHECK-NEXT: 00000010         .text  00000000 $t
diff --git a/test/MC/ARM/multi-section-mapping.s b/test/MC/ARM/multi-section-mapping.s
new file mode 100644
index 0000000..f7c4e89
--- /dev/null
+++ b/test/MC/ARM/multi-section-mapping.s
@@ -0,0 +1,35 @@
+@ RUN: llvm-mc -triple=arm-linux-gnueabi -filetype=obj < %s | llvm-objdump -t - | FileCheck %s
+
+        .text
+        add r0, r0, r0
+
+@ .wibble should *not* inherit .text's mapping symbol. It's a completely different section.
+        .section .wibble
+        add r0, r0, r0
+
+@ A section should be able to start with a $t
+        .section .starts_thumb
+        .thumb
+        adds r0, r0, r0
+
+@ A setion should be able to start with a $d
+        .section .starts_data
+        .word 42
+
+@ Changing back to .text should not emit a redundant $a
+        .text
+        .arm
+        add r0, r0, r0
+
+@ With all those constraints, we want:
+@   + .text to have $a at 0 and no others
+@   + .wibble to have $a at 0
+@   + .starts_thumb to have $t at 0
+@   + .starts_data to have $d at 0
+
+@ CHECK: 00000000 .text 00000000 $a
+@ CHECK-NEXT: 00000000 .wibble 00000000 $a
+@ CHECK-NEXT: 00000000 .starts_data 00000000 $d
+@ CHECK-NEXT: 00000000 .starts_thumb 00000000 $t
+@ CHECK-NOT: ${{[adt]}}
+
diff --git a/test/MC/ARM/relocated-mapping.s b/test/MC/ARM/relocated-mapping.s
new file mode 100644
index 0000000..3bed14c
--- /dev/null
+++ b/test/MC/ARM/relocated-mapping.s
@@ -0,0 +1,11 @@
+@ RUN: llvm-mc -triple=arm-linux-gnueabi -filetype=obj < %s | llvm-objdump -t - | FileCheck %s
+
+@ Implementation-detail test (unfortunately): values that are relocated do not
+@ go via MCStreamer::EmitBytes; make sure they still emit a mapping symbol.
+        add r0, r0, r0
+        .word somewhere
+        add r0, r0, r0
+
+@ CHECK: 00000000 .text 00000000 $a
+@ CHECK-NEXT: 00000008 .text 00000000 $a
+@ CHECK-NEXT: 00000004 .text 00000000 $d