Relax address updates in the eh_frame section.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122591 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCAssembler.cpp b/lib/MC/MCAssembler.cpp
index 030ff98..5b29149 100644
--- a/lib/MC/MCAssembler.cpp
+++ b/lib/MC/MCAssembler.cpp
@@ -323,6 +323,8 @@
 
   case MCFragment::FT_Dwarf:
     return cast<MCDwarfLineAddrFragment>(F).getContents().size();
+  case MCFragment::FT_DwarfFrame:
+    return cast<MCDwarfCallFrameFragment>(F).getContents().size();
   }
 
   assert(0 && "invalid fragment kind");
@@ -453,6 +455,11 @@
     OW->WriteBytes(OF.getContents().str());
     break;
   }
+  case MCFragment::FT_DwarfFrame: {
+    const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
+    OW->WriteBytes(CF.getContents().str());
+    break;
+  }
   }
 
   assert(OW->getStream().tell() - Start == FragmentSize);
@@ -712,6 +719,21 @@
   return OldSize != Data.size();
 }
 
+bool MCAssembler::RelaxDwarfCallFrameFragment(MCAsmLayout &Layout,
+                                              MCDwarfCallFrameFragment &DF) {
+  int64_t AddrDelta = 0;
+  uint64_t OldSize = DF.getContents().size();
+  bool IsAbs = DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, Layout);
+  (void)IsAbs;
+  assert(IsAbs);
+  SmallString<8> &Data = DF.getContents();
+  Data.clear();
+  raw_svector_ostream OSE(Data);
+  MCDwarfFrameEmitter::EncodeAdvanceLoc(AddrDelta, OSE);
+  OSE.flush();
+  return OldSize != Data.size();
+}
+
 bool MCAssembler::LayoutSectionOnce(MCAsmLayout &Layout,
                                     MCSectionData &SD) {
   MCFragment *FirstInvalidFragment = NULL;
@@ -730,9 +752,14 @@
       relaxedFrag = RelaxDwarfLineAddr(Layout,
                                        *cast<MCDwarfLineAddrFragment>(it2));
       break;
-        case MCFragment::FT_LEB:
-          relaxedFrag = RelaxLEB(Layout, *cast<MCLEBFragment>(it2));
-          break;
+    case MCFragment::FT_DwarfFrame:
+      relaxedFrag =
+        RelaxDwarfCallFrameFragment(Layout,
+                                    *cast<MCDwarfCallFrameFragment>(it2));
+      break;
+    case MCFragment::FT_LEB:
+      relaxedFrag = RelaxLEB(Layout, *cast<MCLEBFragment>(it2));
+      break;
     }
     // Update the layout, and remember that we relaxed.
     if (relaxedFrag && !FirstInvalidFragment)
@@ -789,6 +816,7 @@
   case MCFragment::FT_Inst:  OS << "MCInstFragment"; break;
   case MCFragment::FT_Org:   OS << "MCOrgFragment"; break;
   case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
+  case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
   case MCFragment::FT_LEB:   OS << "MCLEBFragment"; break;
   }
 
@@ -855,6 +883,12 @@
        << " LineDelta:" << OF->getLineDelta();
     break;
   }
+  case MCFragment::FT_DwarfFrame:  {
+    const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this);
+    OS << "\n       ";
+    OS << " AddrDelta:" << CF->getAddrDelta();
+    break;
+  }
   case MCFragment::FT_LEB: {
     const MCLEBFragment *LF = cast<MCLEBFragment>(this);
     OS << "\n       ";
diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index 6e59a58..08d327a 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/lib/MC/MCDwarf.cpp
@@ -460,12 +460,7 @@
     if (BaseLabel && Label) {
       MCSymbol *ThisSym = Label;
       if (ThisSym != BaseLabel) {
-        // FIXME: We should relax this instead of using a DW_CFA_advance_loc4
-        // for every address change!
-        streamer.EmitIntValue(dwarf::DW_CFA_advance_loc4, 1);
-        const MCExpr *Length = MakeStartMinusEndExpr(streamer, *BaseLabel,
-                                                     *ThisSym, 0);
-        streamer.EmitValue(Length, 4);
+        streamer.EmitDwarfAdvanceFrameAddr(BaseLabel, ThisSym);
         BaseLabel = ThisSym;
       }
     }
@@ -748,3 +743,30 @@
   if (fdeEnd)
     streamer.EmitLabel(fdeEnd);
 }
+
+void MCDwarfFrameEmitter::EmitAdvanceLoc(MCStreamer &Streamer,
+                                         uint64_t AddrDelta) {
+  SmallString<256> Tmp;
+  raw_svector_ostream OS(Tmp);
+  MCDwarfFrameEmitter::EncodeAdvanceLoc(AddrDelta, OS);
+  Streamer.EmitBytes(OS.str(), /*AddrSpace=*/0);
+}
+
+void MCDwarfFrameEmitter::EncodeAdvanceLoc(uint64_t AddrDelta,
+                                           raw_ostream &OS) {
+  // FIXME: Assumes the code alignment factor is 1.
+  if (isUIntN(6, AddrDelta)) {
+    uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
+    OS << Opcode;
+  } else if (isUInt<8>(AddrDelta)) {
+    OS << uint8_t(dwarf::DW_CFA_advance_loc1);
+    OS << uint8_t(AddrDelta);
+  } else if (isUInt<16>(AddrDelta)) {
+    OS << uint8_t(dwarf::DW_CFA_advance_loc2);
+    OS << uint16_t(AddrDelta);
+  } else {
+    assert(isUInt<32>(AddrDelta));
+    OS << uint8_t(dwarf::DW_CFA_advance_loc4);
+    OS << uint32_t(AddrDelta);
+  }
+}
diff --git a/lib/MC/MCObjectStreamer.cpp b/lib/MC/MCObjectStreamer.cpp
index af102ec..b428e87 100644
--- a/lib/MC/MCObjectStreamer.cpp
+++ b/lib/MC/MCObjectStreamer.cpp
@@ -190,6 +190,28 @@
   getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, IF->getFixups());
 }
 
+static const MCExpr *BuildSymbolDiff(MCContext &Context,
+                                     const MCSymbol *A, const MCSymbol *B) {
+  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
+  const MCExpr *ARef =
+    MCSymbolRefExpr::Create(A, Variant, Context);
+  const MCExpr *BRef =
+    MCSymbolRefExpr::Create(B, Variant, Context);
+  const MCExpr *AddrDelta =
+    MCBinaryExpr::Create(MCBinaryExpr::Sub, ARef, BRef, Context);
+  return AddrDelta;
+}
+
+static const MCExpr *ForceExpAbs(MCObjectStreamer *Streamer,
+                                  MCContext &Context, const MCExpr* Expr) {
+ if (Context.getAsmInfo().hasAggressiveSymbolFolding())
+   return Expr;
+
+ MCSymbol *ABS = Context.CreateTempSymbol();
+ Streamer->EmitAssignment(ABS, Expr);
+ return MCSymbolRefExpr::Create(ABS, Context);
+}
+
 void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
                                                 const MCSymbol *LastLabel,
                                                 const MCSymbol *Label) {
@@ -198,27 +220,28 @@
     EmitDwarfSetLineAddr(LineDelta, Label, PointerSize);
     return;
   }
-  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
-  const MCExpr *LabelRef =
-    MCSymbolRefExpr::Create(Label, Variant, getContext());
-  const MCExpr *LastLabelRef =
-    MCSymbolRefExpr::Create(LastLabel, Variant, getContext());
-  const MCExpr *AddrDelta =
-    MCBinaryExpr::Create(MCBinaryExpr::Sub, LabelRef, LastLabelRef,
-                         getContext());
+  const MCExpr *AddrDelta = BuildSymbolDiff(getContext(), Label, LastLabel);
   int64_t Res;
   if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
     MCDwarfLineAddr::Emit(this, LineDelta, Res);
     return;
   }
-  if (!getContext().getAsmInfo().hasAggressiveSymbolFolding()) {
-    MCSymbol *ABS = getContext().CreateTempSymbol();
-    EmitAssignment(ABS, AddrDelta);
-    AddrDelta = MCSymbolRefExpr::Create(ABS, getContext());
-  }
+  AddrDelta = ForceExpAbs(this, getContext(), AddrDelta);
   new MCDwarfLineAddrFragment(LineDelta, *AddrDelta, getCurrentSectionData());
 }
 
+void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
+                                                 const MCSymbol *Label) {
+  const MCExpr *AddrDelta = BuildSymbolDiff(getContext(), Label, LastLabel);
+  int64_t Res;
+  if (AddrDelta->EvaluateAsAbsolute(Res, getAssembler())) {
+    MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res);
+    return;
+  }
+  AddrDelta = ForceExpAbs(this, getContext(), AddrDelta);
+  new MCDwarfCallFrameFragment(*AddrDelta, getCurrentSectionData());
+}
+
 void MCObjectStreamer::EmitValueToOffset(const MCExpr *Offset,
                                         unsigned char Value) {
   new MCOrgFragment(*Offset, Value, getCurrentSectionData());