Replace the -unwind-tables option with a per function flag. This is more

LTO friendly as we can now correctly merge files compiled with or without
-fasynchronous-unwind-tables.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132033 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Attributes.h

@@ -67,6 +67,20 @@ const Attributes StackAlignment  = 7<<26; ///< Alignment of stack for
                                           ///alignstack(1))
 const Attributes Hotpatch    = 1<<29;     ///< Function should have special
                                           ///'hotpatch' sequence in prologue
+const Attributes UWTable     = 1<<30;     ///< Function must be in a unwind
+                                          ///table
+
+/// Note that uwtable is about the ABI or the user mandating an entry in the
+/// unwind table. The nounwind attribute is about an exception passing by the
+/// function.
+/// In a theoretical system that uses tables for profiling and sjlj for
+/// exceptions, they would be fully independent. In a normal system that
+/// uses tables for both, the semantics are:
+/// nil                = Needs an entry because an exception might pass by.
+/// nounwind           = No need for an entry
+/// ehframe            = Needs an entry because the ABI says so and because
+///                      an exception might pass by.
+/// ehframe + nounwind = Needs an entry because the ABI says so.
 
 /// @brief Attributes that only apply to function parameters.
 const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
@@ -76,7 +90,7 @@ const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
 const Attributes FunctionOnly = NoReturn | NoUnwind | ReadNone | ReadOnly |
   NoInline | AlwaysInline | OptimizeForSize | StackProtect | StackProtectReq |
   NoRedZone | NoImplicitFloat | Naked | InlineHint | StackAlignment |
-  Hotpatch;
+  Hotpatch | UWTable;
 
 /// @brief Parameter attributes that do not apply to vararg call arguments.
 const Attributes VarArgsIncompatible = StructRet;

include/llvm/Function.h

@@ -253,6 +253,22 @@ public:
     else removeFnAttr(Attribute::NoUnwind);
   }
 
+  /// @brief True if the ABI mandates this function be in a unwind table.
+  bool hasUWTable() const {
+    return hasFnAttr(Attribute::UWTable);
+  }
+  void setHasUWTable(bool HasUWTable = true) {
+    if (HasUWTable)
+      addFnAttr(Attribute::UWTable);
+    else
+      removeFnAttr(Attribute::UWTable);
+  }
+
+  /// @brief True if this function needs in a unwind table.
+  bool needsUnwindTableEntry() const {
+    return hasUWTable() || !doesNotThrow();
+  }
+
   /// @brief Determine if the function returns a structure through first 
   /// pointer argument.
   bool hasStructRetAttr() const {

include/llvm/Target/TargetOptions.h

@@ -125,10 +125,6 @@ namespace llvm {
   /// flag is hidden and is only for debugging the debug info.
   extern bool JITEmitDebugInfoToDisk;
 
-  /// UnwindTablesMandatory - This flag indicates that unwind tables should
-  /// be emitted for all functions.
-  extern bool UnwindTablesMandatory;
-
   /// GuaranteedTailCallOpt - This flag is enabled when -tailcallopt is
   /// specified on the commandline. When the flag is on, participating targets
   /// will perform tail call optimization on all calls which use the fastcc

lib/AsmParser/LLLexer.cpp

@@ -565,6 +565,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(nest);
   KEYWORD(readnone);
   KEYWORD(readonly);
+  KEYWORD(uwtable);
 
   KEYWORD(inlinehint);
   KEYWORD(noinline);

lib/AsmParser/LLParser.cpp

@@ -972,6 +972,7 @@ bool LLParser::ParseOptionalAttrs(unsigned &Attrs, unsigned AttrKind) {
 
     case lltok::kw_noreturn:        Attrs |= Attribute::NoReturn; break;
     case lltok::kw_nounwind:        Attrs |= Attribute::NoUnwind; break;
+    case lltok::kw_uwtable:         Attrs |= Attribute::UWTable; break;
     case lltok::kw_noinline:        Attrs |= Attribute::NoInline; break;
     case lltok::kw_readnone:        Attrs |= Attribute::ReadNone; break;
     case lltok::kw_readonly:        Attrs |= Attribute::ReadOnly; break;

lib/AsmParser/LLToken.h

@@ -87,6 +87,7 @@ namespace lltok {
     kw_nest,
     kw_readnone,
     kw_readonly,
+    kw_uwtable,
 
     kw_inlinehint,
     kw_noinline,

lib/CodeGen/AsmPrinter/ARMException.cpp

@@ -52,7 +52,7 @@ void ARMException::EndModule() {
 /// being emitted immediately after the function entry point.
 void ARMException::BeginFunction(const MachineFunction *MF) {
   Asm->OutStreamer.EmitFnStart();
-  if (!Asm->MF->getFunction()->doesNotThrow() || UnwindTablesMandatory)
+  if (Asm->MF->getFunction()->needsUnwindTableEntry())
     Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
                                                   Asm->getFunctionNumber()));
 }
@@ -60,7 +60,7 @@ void ARMException::BeginFunction(const MachineFunction *MF) {
 /// EndFunction - Gather and emit post-function exception information.
 ///
 void ARMException::EndFunction() {
-  if (Asm->MF->getFunction()->doesNotThrow() && !UnwindTablesMandatory)
+  if (!Asm->MF->getFunction()->needsUnwindTableEntry())
     Asm->OutStreamer.EmitCantUnwind();
   else {
     Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -591,13 +591,9 @@ static bool EmitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
 }
 
 AsmPrinter::CFIMoveType AsmPrinter::needsCFIMoves() {
-  if (MAI->getExceptionHandlingType() == ExceptionHandling::DwarfCFI) {
-    if (UnwindTablesMandatory)
-      return CFI_M_EH;
-
-    if (!MF->getFunction()->doesNotThrow())
-      return CFI_M_EH;
-  }
+  if (MAI->getExceptionHandlingType() == ExceptionHandling::DwarfCFI &&
+      MF->getFunction()->needsUnwindTableEntry())
+    return CFI_M_EH;
 
   if (MMI->hasDebugInfo())
     return CFI_M_Debug;

lib/Target/PowerPC/PPCFrameLowering.cpp

@@ -259,8 +259,7 @@ void PPCFrameLowering::emitPrologue(MachineFunction &MF) const {
   MachineModuleInfo &MMI = MF.getMMI();
   DebugLoc dl;
   bool needsFrameMoves = MMI.hasDebugInfo() ||
-       !MF.getFunction()->doesNotThrow() ||
-       UnwindTablesMandatory;
+    MF.getFunction()->needsUnwindTableEntry();
 
   // Prepare for frame info.
   MCSymbol *FrameLabel = 0;

lib/Target/TargetMachine.cpp

@@ -40,7 +40,6 @@ namespace llvm {
   bool JITExceptionHandling;
   bool JITEmitDebugInfo;
   bool JITEmitDebugInfoToDisk;
-  bool UnwindTablesMandatory;
   Reloc::Model RelocationModel;
   CodeModel::Model CMModel;
   bool GuaranteedTailCallOpt;
@@ -143,11 +142,6 @@ EmitJitDebugInfoToDisk("jit-emit-debug-to-disk",
   cl::desc("Emit debug info objfiles to disk"),
   cl::location(JITEmitDebugInfoToDisk),
   cl::init(false));
-static cl::opt<bool, true>
-EnableUnwindTables("unwind-tables",
-  cl::desc("Generate unwinding tables for all functions"),
-  cl::location(UnwindTablesMandatory),
-  cl::init(false));
 
 static cl::opt<llvm::Reloc::Model, true>
 DefRelocationModel("relocation-model",

lib/Target/X86/X86FrameLowering.cpp

@@ -355,7 +355,7 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF) const {
   MachineModuleInfo &MMI = MF.getMMI();
   X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
   bool needsFrameMoves = MMI.hasDebugInfo() ||
-                          !Fn->doesNotThrow() || UnwindTablesMandatory;
+    Fn->needsUnwindTableEntry();
   uint64_t MaxAlign  = MFI->getMaxAlignment(); // Desired stack alignment.
   uint64_t StackSize = MFI->getStackSize();    // Number of bytes to allocate.
   bool HasFP = hasFP(MF);

lib/Target/XCore/XCoreRegisterInfo.cpp

@@ -68,8 +68,8 @@ unsigned XCoreRegisterInfo::getNumArgRegs(const MachineFunction *MF)
 }
 
 bool XCoreRegisterInfo::needsFrameMoves(const MachineFunction &MF) {
-  return MF.getMMI().hasDebugInfo() || !MF.getFunction()->doesNotThrow() ||
-          UnwindTablesMandatory;
+  return MF.getMMI().hasDebugInfo() ||
+    MF.getFunction()->needsUnwindTableEntry();
 }
 
 const unsigned* XCoreRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF)

lib/VMCore/Attributes.cpp

@@ -36,6 +36,8 @@ std::string Attribute::getAsString(Attributes Attrs) {
     Result += "noreturn ";
   if (Attrs & Attribute::NoUnwind)
     Result += "nounwind ";
+  if (Attrs & Attribute::UWTable)
+    Result += "uwtable ";
   if (Attrs & Attribute::InReg)
     Result += "inreg ";
   if (Attrs & Attribute::NoAlias)

test/CodeGen/X86/hidden-vis-pic.ll

@@ -1,4 +1,4 @@
-; RUN: llc < %s -disable-cfi -mtriple=i386-apple-darwin9 -relocation-model=pic -disable-fp-elim -unwind-tables | FileCheck %s
+; RUN: llc < %s -disable-cfi -mtriple=i386-apple-darwin9 -relocation-model=pic -disable-fp-elim | FileCheck %s
 
 
 
@@ -26,7 +26,7 @@ entry:
 
 @.str = private constant [12 x i8] c"hello world\00", align 1 ; <[12 x i8]*> [#uses=1]
 
-define hidden void @func() nounwind ssp {
+define hidden void @func() nounwind ssp uwtable {
 entry:
   %0 = call i32 @puts(i8* getelementptr inbounds ([12 x i8]* @.str, i64 0, i64 0)) nounwind ; <i32> [#uses=0]
   br label %return
@@ -37,7 +37,7 @@ return:                                           ; preds = %entry
 
 declare i32 @puts(i8*)
 
-define hidden i32 @main() nounwind ssp {
+define hidden i32 @main() nounwind ssp uwtable {
 entry:
   %retval = alloca i32                            ; <i32*> [#uses=1]
   %"alloca point" = bitcast i32 0 to i32          ; <i32> [#uses=0]