From 3660a847f1820d73847539f3959dc069396f8e44 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Wed, 20 Apr 2011 14:01:45 +0000
Subject: [PATCH] Behave like gnu as when a relocation crosses sections.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129850 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/MC/WinCOFFObjectWriter.cpp | 21 +++++++++++++--------
 test/MC/COFF/diff.s            | 28 ++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 8 deletions(-)
 create mode 100644 test/MC/COFF/diff.s

diff --git a/lib/MC/WinCOFFObjectWriter.cpp b/lib/MC/WinCOFFObjectWriter.cpp
index 6ca5d37fc32..fe3342c886b 100644
--- a/lib/MC/WinCOFFObjectWriter.cpp
+++ b/lib/MC/WinCOFFObjectWriter.cpp
@@ -647,13 +647,12 @@ void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
 
   COFFSection *coff_section = SectionMap[&SectionData->getSection()];
   COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
+  const MCSymbolRefExpr *SymA = Target.getSymA();
+  const MCSymbolRefExpr *SymB = Target.getSymB();
+  const bool CrossSection = SymB &&
+    &SymA->getSymbol().getSection() != &SymB->getSymbol().getSection();
 
   if (Target.getSymB()) {
-    if (&Target.getSymA()->getSymbol().getSection()
-     != &Target.getSymB()->getSymbol().getSection()) {
-      llvm_unreachable("Symbol relative relocations are only allowed between "
-                       "symbols in the same section");
-    }
     const MCSymbol *B = &Target.getSymB()->getSymbol();
     MCSymbolData &B_SD = Asm.getSymbolData(*B);
 
@@ -662,7 +661,8 @@ void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
     // In the case where we have SymbA and SymB, we just need to store the delta
     // between the two symbols.  Update FixedValue to account for the delta, and
     // skip recording the relocation.
-    return;
+    if (!CrossSection)
+      return;
   } else {
     FixedValue = Target.getConstant();
   }
@@ -673,7 +673,7 @@ void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
   Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
 
   // Turn relocations for temporary symbols into section relocations.
-  if (coff_symbol->MCData->getSymbol().isTemporary()) {
+  if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
     Reloc.Symb = coff_symbol->Section->Symbol;
     FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
                 + coff_symbol->MCData->getOffset();
@@ -684,7 +684,12 @@ void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
 
   Reloc.Data.VirtualAddress += Fixup.getOffset();
 
-  switch ((unsigned)Fixup.getKind()) {
+  unsigned FixupKind = Fixup.getKind();
+
+  if (CrossSection)
+    FixupKind = FK_PCRel_4;
+
+  switch (FixupKind) {
   case FK_PCRel_4:
   case X86::reloc_riprel_4byte:
   case X86::reloc_riprel_4byte_movq_load:
diff --git a/test/MC/COFF/diff.s b/test/MC/COFF/diff.s
new file mode 100644
index 00000000000..b7db5097fd6
--- /dev/null
+++ b/test/MC/COFF/diff.s
@@ -0,0 +1,28 @@
+// RUN: llvm-mc -filetype=obj -triple i686-pc-mingw32 %s | coff-dump.py | FileCheck %s
+
+	.def	 _foobar;
+	.scl	2;
+	.type	32;
+	.endef
+	.text
+	.globl	_foobar
+	.align	16, 0x90
+_foobar:                                # @foobar
+# BB#0:
+	ret
+
+	.data
+	.globl	_rust_crate             # @rust_crate
+	.align	4
+_rust_crate:
+	.long	_foobar-_rust_crate
+
+
+// CHECK:       Relocations              = [
+// CHECK-NEXT:   0 = {
+// CHECK-NEXT:     VirtualAddress           = 0x0
+// CHECK-NEXT:     SymbolTableIndex         =
+// CHECK-NEXT:     Type                     = IMAGE_REL_I386_REL32 (20)
+// CHECK-NEXT:     SymbolName               = .text
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]