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

4 files changed, 33 insertions, 16 deletions

diff --git a/lib/MC/MCAsmStreamer.cpp b/lib/MC/MCAsmStreamer.cpp
index 12bcb68dd8..d63716a815 100644
--- a/lib/MC/MCAsmStreamer.cpp
+++ b/lib/MC/MCAsmStreamer.cpp
@@ -925,6 +925,8 @@ void MCAsmStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
   }
 
   OS << "\t.cfi_startproc";
+  if (Frame.IsSimple)
+    OS << " simple";
   EmitEOL();
 }
 
diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index 12070f36ea..fe20a6d9a9 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/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 =
-      MAI->getInitialFrameState();
-  EmitCFIInstructions(streamer, Instructions, NULL);
+  if (!IsSimple) {
+    const std::vector<MCCFIInstruction> &Instructions =
+        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 getTombstoneKey() { return CIEKey(0, -1, 0, false); }
+    static const CIEKey getEmptyKey() { return CIEKey(0, 0, -1, false, 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);
 
diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index a1d016261f..10f4fbb04e 100644
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/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;
 }
 
diff --git a/lib/MC/MCStreamer.cpp b/lib/MC/MCStreamer.cpp
index 8cbfc5c83e..996be956e9 100644
--- a/lib/MC/MCStreamer.cpp
+++ b/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);