Allow using .cfi_startproc without a leading symbol.

This is possible now that we don't produce .eh symbols. This fixes pr19430.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211502 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCDwarf.h

@@ -466,14 +466,12 @@ public:
 struct MCDwarfFrameInfo {
   MCDwarfFrameInfo()
       : Begin(nullptr), End(nullptr), Personality(nullptr), Lsda(nullptr),
-        Function(nullptr), Instructions(), PersonalityEncoding(),
-        LsdaEncoding(0), CompactUnwindEncoding(0), IsSignalFrame(false),
-        IsSimple(false) {}
+        Instructions(), PersonalityEncoding(), LsdaEncoding(0),
+        CompactUnwindEncoding(0), IsSignalFrame(false), IsSimple(false) {}
   MCSymbol *Begin;
   MCSymbol *End;
   const MCSymbol *Personality;
   const MCSymbol *Lsda;
-  const MCSymbol *Function;
   std::vector<MCCFIInstruction> Instructions;
   unsigned PersonalityEncoding;
   unsigned LsdaEncoding;

include/llvm/MC/MCStreamer.h

@@ -164,8 +164,6 @@ class MCStreamer {
   void setCurrentW64UnwindInfo(MCWin64EHUnwindInfo *Frame);
   void EnsureValidW64UnwindInfo();
 
-  MCSymbol *LastSymbol;
-
   // SymbolOrdering - Tracks an index to represent the order
   // a symbol was emitted in. Zero means we did not emit that symbol.
   DenseMap<const MCSymbol *, unsigned> SymbolOrdering;

lib/MC/MCDwarf.cpp

@@ -1297,7 +1297,7 @@ void FrameEmitterImpl::EmitCompactUnwind(MCStreamer &Streamer,
   unsigned FDEEncoding = MOFI->getFDEEncoding();
   unsigned Size = getSizeForEncoding(Streamer, FDEEncoding);
   if (VerboseAsm) Streamer.AddComment("Range Start");
-  Streamer.EmitSymbolValue(Frame.Function, Size);
+  Streamer.EmitSymbolValue(Frame.Begin, Size);
 
   // Range Length
   const MCExpr *Range = MakeStartMinusEndExpr(Streamer, *Frame.Begin,

lib/MC/MCStreamer.cpp

@@ -37,7 +37,7 @@ void MCTargetStreamer::finish() {}
 void MCTargetStreamer::emitAssignment(MCSymbol *Symbol, const MCExpr *Value) {}
 
 MCStreamer::MCStreamer(MCContext &Ctx)
-    : Context(Ctx), CurrentW64UnwindInfo(nullptr), LastSymbol(nullptr) {
+    : Context(Ctx), CurrentW64UnwindInfo(nullptr) {
   SectionStack.push_back(std::pair<MCSectionSubPair, MCSectionSubPair>());
 }
 
@@ -51,7 +51,6 @@ void MCStreamer::reset() {
     delete W64UnwindInfos[i];
   W64UnwindInfos.clear();
   CurrentW64UnwindInfo = nullptr;
-  LastSymbol = nullptr;
   SectionStack.clear();
   SectionStack.push_back(std::pair<MCSectionSubPair, MCSectionSubPair>());
 }
@@ -234,7 +233,6 @@ void MCStreamer::EmitLabel(MCSymbol *Symbol) {
   assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
   assert(getCurrentSection().first && "Cannot emit before setting section!");
   AssignSection(Symbol, getCurrentSection().first);
-  LastSymbol = Symbol;
 
   MCTargetStreamer *TS = getTargetStreamer();
   if (TS)
@@ -245,7 +243,6 @@ void MCStreamer::EmitDebugLabel(MCSymbol *Symbol) {
   assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
   assert(getCurrentSection().first && "Cannot emit before setting section!");
   AssignSection(Symbol, getCurrentSection().first);
-  LastSymbol = Symbol;
 }
 
 void MCStreamer::EmitCompactUnwindEncoding(uint32_t CompactUnwindEncoding) {
@@ -274,11 +271,6 @@ void MCStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
 }
 
 void MCStreamer::RecordProcStart(MCDwarfFrameInfo &Frame) {
-  // Report an error if we haven't seen a symbol yet where we'd bind
-  // .cfi_startproc.
-  if (!LastSymbol)
-    report_fatal_error("No symbol to start a frame");
-  Frame.Function = LastSymbol;
   // We need to create a local symbol to avoid relocations.
   Frame.Begin = getContext().CreateTempSymbol();
   EmitLabel(Frame.Begin);

test/MC/AsmParser/cfi-invalid-startproc.s

@@ -1,16 +0,0 @@
-# RUN: not llvm-mc -triple=x86_64-apple-macosx10.8 -filetype=obj -o %t %s 2>&1 | FileCheck %s
-# Check that the cfi_startproc is declared after the beginning of
-# a procedure, otherwise it will reference an invalid symbol for
-# emitting the relocation.
-# <rdar://problem/15939159>
-
-# CHECK: No symbol to start a frame
-.text
-.cfi_startproc
-.globl _someFunction
-_someFunction:
-.cfi_def_cfa_offset 16
-.cfi_offset %rbp, -16
-.cfi_def_cfa_register rbp
-  ret
-.cfi_endproc

test/MC/ELF/pr19430.s

@@ -0,0 +1,14 @@
+// RUN: llvm-mc -triple x86_64-pc-linux-gnu %s -filetype=obj -o - | llvm-readobj -r | FileCheck %s
+
+// Test that we can use .cfi_startproc without a global symbol.
+
+.text
+.space 1000
+.cfi_startproc
+ .cfi_endproc
+
+// CHECK:      Relocations [
+// CHECK-NEXT:   Section (5) .rela.eh_frame {
+// CHECK-NEXT:     0x20 R_X86_64_PC32 .text 0x3E8
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]