From e3a0e987f3d4f07512cdb64b9034369f966cb448 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Tue, 10 May 2011 20:59:42 +0000
Subject: [PATCH] On MachO, unlike ELF, there should be no relocation to
 produce the CIE pointer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131149 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/MC/MCDwarf.cpp          | 25 ++++++++++++++++--------
 test/MC/MachO/debug_frame.s | 38 +++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 8 deletions(-)
 create mode 100644 test/MC/MachO/debug_frame.s

diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index d0eaf2074c6..7cf6cddd4fd 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/lib/MC/MCDwarf.cpp
@@ -502,11 +502,12 @@ namespace {
     int CIENum;
     bool UsingCFI;
     bool IsEH;
+    const MCSymbol *SectionStart;
 
   public:
-    FrameEmitterImpl(bool usingCFI, bool isEH) : CFAOffset(0), CIENum(0),
-                                                 UsingCFI(usingCFI),
-                                                 IsEH(isEH) {
+    FrameEmitterImpl(bool usingCFI, bool isEH, const MCSymbol *sectionStart) :
+      CFAOffset(0), CIENum(0), UsingCFI(usingCFI), IsEH(isEH),
+      SectionStart(sectionStart) {
     }
 
     const MCSymbol &EmitCIE(MCStreamer &streamer,
@@ -737,9 +738,9 @@ MCSymbol *FrameEmitterImpl::EmitFDE(MCStreamer &streamer,
   MCContext &context = streamer.getContext();
   MCSymbol *fdeStart = context.CreateTempSymbol();
   MCSymbol *fdeEnd = context.CreateTempSymbol();
-  const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
+  const TargetAsmInfo &TAsmInfo = context.getTargetAsmInfo();
 
-  if (!asmInfo.isFunctionEHFrameSymbolPrivate() && IsEH) {
+  if (!TAsmInfo.isFunctionEHFrameSymbolPrivate() && IsEH) {
     MCSymbol *EHSym = context.GetOrCreateSymbol(
       frame.Function->getName() + Twine(".eh"));
     streamer.EmitEHSymAttributes(frame.Function, EHSym);
@@ -751,15 +752,21 @@ MCSymbol *FrameEmitterImpl::EmitFDE(MCStreamer &streamer,
   streamer.EmitAbsValue(Length, 4);
 
   streamer.EmitLabel(fdeStart);
+
   // CIE Pointer
+  const MCAsmInfo &asmInfo = context.getAsmInfo();
   if (IsEH) {
     const MCExpr *offset = MakeStartMinusEndExpr(streamer, cieStart, *fdeStart,
                                                  0);
     streamer.EmitAbsValue(offset, 4);
+  } else if (!asmInfo.doesDwarfRequireRelocationForSectionOffset()) {
+    const MCExpr *offset = MakeStartMinusEndExpr(streamer, *SectionStart,
+                                                 cieStart, 0);
+    streamer.EmitAbsValue(offset, 4);
   } else {
     streamer.EmitSymbolValue(&cieStart, 4);
   }
-  unsigned fdeEncoding = asmInfo.getFDEEncoding(UsingCFI);
+  unsigned fdeEncoding = TAsmInfo.getFDEEncoding(UsingCFI);
   unsigned size = getSizeForEncoding(streamer, fdeEncoding);
 
   // PC Begin
@@ -840,15 +847,17 @@ namespace llvm {
 void MCDwarfFrameEmitter::Emit(MCStreamer &streamer,
                                bool usingCFI,
                                bool isEH) {
-  const MCContext &context = streamer.getContext();
+  MCContext &context = streamer.getContext();
   const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
   const MCSection &section = isEH ?
     *asmInfo.getEHFrameSection() : *asmInfo.getDwarfFrameSection();
   streamer.SwitchSection(&section);
+  MCSymbol *SectionStart = context.CreateTempSymbol();
+  streamer.EmitLabel(SectionStart);
 
   MCSymbol *fdeEnd = NULL;
   DenseMap<CIEKey, const MCSymbol*> CIEStarts;
-  FrameEmitterImpl Emitter(usingCFI, isEH);
+  FrameEmitterImpl Emitter(usingCFI, isEH, SectionStart);
 
   const MCSymbol *DummyDebugKey = NULL;
   for (unsigned i = 0, n = streamer.getNumFrameInfos(); i < n; ++i) {
diff --git a/test/MC/MachO/debug_frame.s b/test/MC/MachO/debug_frame.s
new file mode 100644
index 00000000000..47264ef8799
--- /dev/null
+++ b/test/MC/MachO/debug_frame.s
@@ -0,0 +1,38 @@
+// RUN: llvm-mc -triple i386-apple-darwin %s -filetype=obj -o - | macho-dump | FileCheck %s
+
+// Check that we don't produce a relocation for the CIE pointer and therefore
+// we have only one relocation in __debug_frame.
+
+	.section	__TEXT,__text,regular,pure_instructions
+	.globl	_f
+	.align	4, 0x90
+_f:                                     ## @f
+Ltmp0:
+	.cfi_startproc
+## BB#0:                                ## %entry
+	movl	$42, %eax
+	ret
+Ltmp1:
+	.cfi_endproc
+Leh_func_end0:
+
+	.cfi_sections .debug_frame
+Ltext_end:
+
+// CHECK:       (('section_name', '__debug_frame\x00\x00\x00')
+// CHECK-NEXT:   ('segment_name', '__DWARF\x00\x00\x00\x00\x00\x00\x00\x00\x00')
+// CHECK-NEXT:   ('address', 8)
+// CHECK-NEXT:   ('size', 36)
+// CHECK-NEXT:   ('offset', 332)
+// CHECK-NEXT:   ('alignment', 2)
+// CHECK-NEXT:   ('reloc_offset', 368)
+// CHECK-NEXT:   ('num_reloc', 1)
+// CHECK-NEXT:   ('flags', 0x2000000)
+// CHECK-NEXT:   ('reserved1', 0)
+// CHECK-NEXT:   ('reserved2', 0)
+// CHECK-NEXT:  ),
+// CHECK-NEXT: ('_relocations', [
+// CHECK-NEXT:   # Relocation 0
+// CHECK-NEXT:   (('word-0', 0x1c),
+// CHECK-NEXT:    ('word-1', 0x4000001)),
+// CHECK-NEXT: ])