From fc6e0f6f8721a59d788ba07fef8b4f3a5c07ae9a Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Wed, 15 Oct 2014 19:30:18 +0000
Subject: [PATCH] Allow forward references to section symbols.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219835 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/MC/MCContext.cpp       |  9 ++++++++-
 test/MC/ELF/section-sym2.s | 28 ++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 test/MC/ELF/section-sym2.s

diff --git a/lib/MC/MCContext.cpp b/lib/MC/MCContext.cpp
index 3ac8d658873..ea6db142fd7 100644
--- a/lib/MC/MCContext.cpp
+++ b/lib/MC/MCContext.cpp
@@ -119,11 +119,18 @@ MCSymbol *MCContext::getOrCreateSectionSymbol(const MCSectionELF &Section) {
     return Sym;
 
   StringRef Name = Section.getSectionName();
+
+  StringMapEntry<MCSymbol*> &Entry = Symbols.GetOrCreateValue(Name);
+  MCSymbol *OldSym = Entry.getValue();
+  if (OldSym && OldSym->isUndefined()) {
+    Sym = OldSym;
+    return OldSym;
+  }
+
   StringMapEntry<bool> *NameEntry = &UsedNames.GetOrCreateValue(Name);
   NameEntry->setValue(true);
   Sym = new (*this) MCSymbol(NameEntry->getKey(), /*isTemporary*/ false);
 
-  StringMapEntry<MCSymbol*> &Entry = Symbols.GetOrCreateValue(Name);
   if (!Entry.getValue())
     Entry.setValue(Sym);
 
diff --git a/test/MC/ELF/section-sym2.s b/test/MC/ELF/section-sym2.s
new file mode 100644
index 00000000000..acdb7d9547d
--- /dev/null
+++ b/test/MC/ELF/section-sym2.s
@@ -0,0 +1,28 @@
+// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj  -t -r --expand-relocs | FileCheck %s
+
+// Test that we can forward reference a section.
+
+mov .rodata, %rsi
+.section .rodata
+
+// CHECK:Relocations [
+// CHECK:  Section (2) .rela.text {
+// CHECK:    Relocation {
+// CHECK:      Offset: 0x4
+// CHECK:      Type: R_X86_64_32S (11)
+// CHECK:      Symbol: .rodata
+// CHECK:      Addend: 0x0
+// CHECK:    }
+// CHECK:  }
+// CHECK:]
+
+// There is only one .rodata symbol
+
+// CHECK:Symbols [
+// CHECK-NOT:    Name: .rodata
+// CHECK:        Name: .rodata
+// CHECK-NEXT:   Value: 0x0
+// CHECK-NEXT:   Size: 0
+// CHECK-NEXT:   Binding: Local (0x0)
+// CHECK-NEXT:   Type: Section (0x3)
+// CHECK-NOT:    Name: .rodata