MC: Add support for .cfi_startproc simple

This commit allows LLVM MC to process .cfi_startproc directives when
they are followed by an additional `simple' identifier. This signals to
elide the emission of target specific CFI instructions that would
normally occur initially.

This fixes PR16587.

Differential Revision: http://llvm-reviews.chandlerc.com/D2624


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200227 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCDwarf.h

@@ -438,7 +438,7 @@ struct MCDwarfFrameInfo {
   MCDwarfFrameInfo()
       : Begin(0), End(0), Personality(0), Lsda(0), Function(0), Instructions(),
         PersonalityEncoding(), LsdaEncoding(0), CompactUnwindEncoding(0),
-        IsSignalFrame(false) {}
+        IsSignalFrame(false), IsSimple(false) {}
   MCSymbol *Begin;
   MCSymbol *End;
   const MCSymbol *Personality;
@@ -449,6 +449,7 @@ struct MCDwarfFrameInfo {
   unsigned LsdaEncoding;
   uint32_t CompactUnwindEncoding;
   bool IsSignalFrame;
+  bool IsSimple;
 };
 
 class MCDwarfFrameEmitter {

include/llvm/MC/MCStreamer.h

@@ -626,7 +626,7 @@ public:
 
   virtual void EmitCompactUnwindEncoding(uint32_t CompactUnwindEncoding);
   virtual void EmitCFISections(bool EH, bool Debug);
-  void EmitCFIStartProc();
+  void EmitCFIStartProc(bool IsSimple);
   void EmitCFIEndProc();
   virtual void EmitCFIDefCfa(int64_t Register, int64_t Offset);
   virtual void EmitCFIDefCfaOffset(int64_t Offset);

lib/CodeGen/AsmPrinter/DwarfCFIException.cpp

@@ -113,7 +113,7 @@ void DwarfCFIException::beginFunction(const MachineFunction *MF) {
   if (!shouldEmitPersonality && !shouldEmitMoves)
     return;
 
-  Asm->OutStreamer.EmitCFIStartProc();
+  Asm->OutStreamer.EmitCFIStartProc(/*IsSimple=*/false);
 
   // Indicate personality routine, if any.
   if (!shouldEmitPersonality)

lib/MC/MCAsmStreamer.cpp

@@ -925,6 +925,8 @@ void MCAsmStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
   }
 
   OS << "\t.cfi_startproc";
+  if (Frame.IsSimple)
+    OS << " simple";
   EmitEOL();
 }
 

lib/MC/MCDwarf.cpp

@@ -889,7 +889,8 @@ namespace {
                             unsigned personalityEncoding,
                             const MCSymbol *lsda,
                             bool IsSignalFrame,
-                            unsigned lsdaEncoding);
+                            unsigned lsdaEncoding,
+                            bool IsSimple);
     MCSymbol *EmitFDE(MCStreamer &streamer,
                       const MCSymbol &cieStart,
                       const MCDwarfFrameInfo &frame);
@@ -1199,7 +1200,8 @@ const MCSymbol &FrameEmitterImpl::EmitCIE(MCStreamer &streamer,
                                           unsigned personalityEncoding,
                                           const MCSymbol *lsda,
                                           bool IsSignalFrame,
-                                          unsigned lsdaEncoding) {
+                                          unsigned lsdaEncoding,
+                                          bool IsSimple) {
   MCContext &context = streamer.getContext();
   const MCRegisterInfo *MRI = context.getRegisterInfo();
   const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
@@ -1298,9 +1300,11 @@ const MCSymbol &FrameEmitterImpl::EmitCIE(MCStreamer &streamer,
   // Initial Instructions
 
   const MCAsmInfo *MAI = context.getAsmInfo();
-  const std::vector<MCCFIInstruction> &Instructions =
+  if (!IsSimple) {
-      MAI->getInitialFrameState();
+    const std::vector<MCCFIInstruction> &Instructions =
-  EmitCFIInstructions(streamer, Instructions, NULL);
+        MAI->getInitialFrameState();
+    EmitCFIInstructions(streamer, Instructions, NULL);
+  }
 
   // Padding
   streamer.EmitValueToAlignment(IsEH ? 4 : MAI->getPointerSize());
@@ -1386,18 +1390,20 @@ MCSymbol *FrameEmitterImpl::EmitFDE(MCStreamer &streamer,
 
 namespace {
   struct CIEKey {
-    static const CIEKey getEmptyKey() { return CIEKey(0, 0, -1, false); }
+    static const CIEKey getEmptyKey() { return CIEKey(0, 0, -1, false, false); }
-    static const CIEKey getTombstoneKey() { return CIEKey(0, -1, 0, false); }
+    static const CIEKey getTombstoneKey() { return CIEKey(0, -1, 0, false, false); }
 
     CIEKey(const MCSymbol* Personality_, unsigned PersonalityEncoding_,
-           unsigned LsdaEncoding_, bool IsSignalFrame_) :
+           unsigned LsdaEncoding_, bool IsSignalFrame_, bool IsSimple_) :
       Personality(Personality_), PersonalityEncoding(PersonalityEncoding_),
-      LsdaEncoding(LsdaEncoding_), IsSignalFrame(IsSignalFrame_) {
+      LsdaEncoding(LsdaEncoding_), IsSignalFrame(IsSignalFrame_),
+      IsSimple(IsSimple_) {
     }
     const MCSymbol* Personality;
     unsigned PersonalityEncoding;
     unsigned LsdaEncoding;
     bool IsSignalFrame;
+    bool IsSimple;
   };
 }
 
@@ -1414,14 +1420,16 @@ namespace llvm {
       return static_cast<unsigned>(hash_combine(Key.Personality,
                                                 Key.PersonalityEncoding,
                                                 Key.LsdaEncoding,
-                                                Key.IsSignalFrame));
+                                                Key.IsSignalFrame,
+                                                Key.IsSimple));
     }
     static bool isEqual(const CIEKey &LHS,
                         const CIEKey &RHS) {
       return LHS.Personality == RHS.Personality &&
         LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
         LHS.LsdaEncoding == RHS.LsdaEncoding &&
-        LHS.IsSignalFrame == RHS.IsSignalFrame;
+        LHS.IsSignalFrame == RHS.IsSignalFrame &&
+        LHS.IsSimple == RHS.IsSimple;
     }
   };
 }
@@ -1465,13 +1473,14 @@ void MCDwarfFrameEmitter::Emit(MCStreamer &Streamer, MCAsmBackend *MAB,
   for (unsigned i = 0, n = FrameArray.size(); i < n; ++i) {
     const MCDwarfFrameInfo &Frame = FrameArray[i];
     CIEKey Key(Frame.Personality, Frame.PersonalityEncoding,
-               Frame.LsdaEncoding, Frame.IsSignalFrame);
+               Frame.LsdaEncoding, Frame.IsSignalFrame, Frame.IsSimple);
     const MCSymbol *&CIEStart = IsEH ? CIEStarts[Key] : DummyDebugKey;
     if (!CIEStart)
       CIEStart = &Emitter.EmitCIE(Streamer, Frame.Personality,
                                   Frame.PersonalityEncoding, Frame.Lsda,
                                   Frame.IsSignalFrame,
-                                  Frame.LsdaEncoding);
+                                  Frame.LsdaEncoding,
+                                  Frame.IsSimple);
 
     FDEEnd = Emitter.EmitFDE(Streamer, *CIEStart, Frame);
 

lib/MC/MCParser/AsmParser.cpp

@@ -2796,9 +2796,14 @@ bool AsmParser::parseDirectiveCFISections() {
 }
 
 /// parseDirectiveCFIStartProc
-/// ::= .cfi_startproc
+/// ::= .cfi_startproc [simple]
 bool AsmParser::parseDirectiveCFIStartProc() {
-  getStreamer().EmitCFIStartProc();
+  StringRef Simple;
+  if (getLexer().isNot(AsmToken::EndOfStatement))
+    if (parseIdentifier(Simple) || Simple != "simple")
+      return TokError("unexpected token in .cfi_startproc directive");
+
+  getStreamer().EmitCFIStartProc(!Simple.empty());
   return false;
 }
 

lib/MC/MCStreamer.cpp

@@ -248,12 +248,13 @@ void MCStreamer::EmitCFISections(bool EH, bool Debug) {
   EmitDebugFrame = Debug;
 }
 
-void MCStreamer::EmitCFIStartProc() {
+void MCStreamer::EmitCFIStartProc(bool IsSimple) {
   MCDwarfFrameInfo *CurFrame = getCurrentFrameInfo();
   if (CurFrame && !CurFrame->End)
     report_fatal_error("Starting a frame before finishing the previous one!");
 
   MCDwarfFrameInfo Frame;
+  Frame.IsSimple = IsSimple;
   EmitCFIStartProcImpl(Frame);
 
   FrameInfos.push_back(Frame);

test/MC/ELF/cfi.s

@@ -212,6 +212,11 @@ f36:
         nop
         .cfi_endproc
 
+f37:
+        .cfi_startproc simple
+        nop
+        .cfi_endproc
+
 // CHECK:        Section {
 // CHECK:          Index: 4
 // CHECK-NEXT:     Name: .eh_frame
@@ -221,7 +226,7 @@ f36:
 // CHECK-NEXT:     ]
 // CHECK-NEXT:     Address: 0x0
 // CHECK-NEXT:     Offset: 0x68
-// CHECK-NEXT:     Size: 1736
+// CHECK-NEXT:     Size: 1776
 // CHECK-NEXT:     Link: 0
 // CHECK-NEXT:     Info: 0
 // CHECK-NEXT:     AddressAlignment: 8
@@ -337,7 +342,9 @@ f36:
 // CHECK-NEXT:       0690: 00000000 1C000000 00000000 017A5052
 // CHECK-NEXT:       06A0: 00017810 0A980000 00000000 00001B0C
 // CHECK-NEXT:       06B0: 07089001 10000000 24000000 00000000
-// CHECK-NEXT:       06C0: 01000000 00000000
+// CHECK-NEXT:       06C0: 01000000 00000000 10000000 00000000
+// CHECK-NEXT:       06D0: 017A5200 01781001 1B000000 10000000
+// CHECK-NEXT:       06E0: 18000000 00000000 01000000 00000000
 // CHECK-NEXT:     )
 // CHECK-NEXT:   }
 
@@ -348,8 +355,8 @@ f36:
 // CHECK-NEXT:     Flags [
 // CHECK-NEXT:     ]
 // CHECK-NEXT:     Address: 0x0
-// CHECK-NEXT:     Offset: 0xE30
+// CHECK-NEXT:     Offset: 0xE70
-// CHECK-NEXT:     Size: 1728
+// CHECK-NEXT:     Size: 1752
 // CHECK-NEXT:     Link: 7
 // CHECK-NEXT:     Info: 4
 // CHECK-NEXT:     AddressAlignment: 8
@@ -427,5 +434,6 @@ f36:
 // CHECK-NEXT:       0x688 R_X86_64_PC32 .text 0x21
 // CHECK-NEXT:       0x6A6 R_X86_64_PC64 foo   0x0
 // CHECK-NEXT:       0x6BC R_X86_64_PC32 .text 0x22
+// CHECK-NEXT:       0x6E4 R_X86_64_PC32 .text 0x23
 // CHECK-NEXT:     ]
 // CHECK:        }