AArch64: work around ld64 bug more aggressively.

ld64 currently mishandles internal pointer relocations (i.e.
ARM64_RELOC_UNSIGNED referred to by section & offset rather than symbol). The
existing __cfstring clause was an early discovery and workaround for this, but
the problem is wider and we should avoid such relocations wherever possible for
now.

This code should be reverted to allowing internal relocations as soon as
possible.

PR23437.

llvm-svn: 237621

llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp

@@ -130,15 +130,14 @@ static bool canUseLocalRelocation(const MCSectionMachO &Section,
   if (RefSec.getType() == MachO::S_CSTRING_LITERALS)
     return false;
 
-  if (RefSec.getSegmentName() == "__DATA" &&
-      RefSec.getSectionName() == "__cfstring")
-    return false;
-
   if (RefSec.getSegmentName() == "__DATA" &&
       RefSec.getSectionName() == "__objc_classrefs")
     return false;
 
-  return true;
+  // FIXME: ld64 currently handles internal pointer-sized relocations
+  // incorrectly (applying the addend twice). We should be able to return true
+  // unconditionally by this point when that's fixed.
+  return false;
 }
 
 void AArch64MachObjectWriter::RecordRelocation(

llvm/test/MC/MachO/AArch64/cfstring.s

@@ -1,24 +0,0 @@
-; RUN: llvm-mc -triple arm64-apple-darwin10 %s -filetype=obj -o - | llvm-readobj -r --expand-relocs | FileCheck %s
-
-; Test that we produce an external relocation. There is no apparent need for it, but
-; ld64 (241.9) produces a corrupt output if we don't.
-
-// CHECK:      Relocations [
-// CHECK-NEXT:   Section __data {
-// CHECK-NEXT:     Relocation {
-// CHECK-NEXT:       Offset: 0x0
-// CHECK-NEXT:       PCRel: 0
-// CHECK-NEXT:       Length: 3
-// CHECK-NEXT:       Extern: 1
-// CHECK-NEXT:       Type: ARM64_RELOC_UNSIGNED (0)
-// CHECK-NEXT:       Symbol: Lfoo
-// CHECK-NEXT:       Scattered: 0
-// CHECK-NEXT:     }
-// CHECK-NEXT:   }
-// CHECK-NEXT: ]
-
-        .section        __DATA,__cfstring
-Lfoo:
-
-        .section        __DATA,__data
-        .quad   Lfoo

llvm/test/MC/MachO/AArch64/ld64-workaround.s

@@ -0,0 +1,68 @@
+; RUN: llvm-mc -triple arm64-apple-darwin10 %s -filetype=obj -o - | llvm-readobj -r --expand-relocs | FileCheck %s
+
+; Test that we produce an external relocation. This is a known and temporary bug
+; in ld64, where it mishandles pointer-sized internal relocations. We should be
+; able to remove this entirely soon.
+
+// CHECK:      Relocations [
+// CHECK-NEXT:   Section __data {
+// CHECK-NEXT:     Relocation {
+// CHECK-NEXT:       Offset: 0x18
+// CHECK-NEXT:       PCRel: 0
+// CHECK-NEXT:       Length: 3
+// CHECK-NEXT:       Extern: 1
+// CHECK-NEXT:       Type: ARM64_RELOC_UNSIGNED (0)
+// CHECK-NEXT:       Symbol: Llit16
+// CHECK-NEXT:       Scattered: 0
+// CHECK-NEXT:     }
+// CHECK-NEXT:     Relocation {
+// CHECK-NEXT:       Offset: 0x10
+// CHECK-NEXT:       PCRel: 0
+// CHECK-NEXT:       Length: 3
+// CHECK-NEXT:       Extern: 1
+// CHECK-NEXT:       Type: ARM64_RELOC_UNSIGNED (0)
+// CHECK-NEXT:       Symbol: Llit8
+// CHECK-NEXT:       Scattered: 0
+// CHECK-NEXT:     }
+// CHECK-NEXT:     Relocation {
+// CHECK-NEXT:       Offset: 0x8
+// CHECK-NEXT:       PCRel: 0
+// CHECK-NEXT:       Length: 3
+// CHECK-NEXT:       Extern: 1
+// CHECK-NEXT:       Type: ARM64_RELOC_UNSIGNED (0)
+// CHECK-NEXT:       Symbol: Llit4
+// CHECK-NEXT:       Scattered: 0
+// CHECK-NEXT:     }
+// CHECK-NEXT:     Relocation {
+// CHECK-NEXT:       Offset: 0x0
+// CHECK-NEXT:       PCRel: 0
+// CHECK-NEXT:       Length: 3
+// CHECK-NEXT:       Extern: 1
+// CHECK-NEXT:       Type: ARM64_RELOC_UNSIGNED (0)
+// CHECK-NEXT:       Symbol: Lcfstring
+// CHECK-NEXT:       Scattered: 0
+// CHECK-NEXT:     }
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]
+
+        .section        __DATA,__cfstring
+Lcfstring:
+
+        .section        __DATA,__literal4,4byte_literals
+Llit4:
+        .word 42
+
+        .section        __DATA,__literal8,8byte_literals
+Llit8:
+        .quad 42
+
+        .section        __DATA,__literal16,16byte_literals
+Llit16:
+        .quad 42
+        .quad 42
+
+        .section        __DATA,__data
+        .quad   Lcfstring
+        .quad   Llit4
+        .quad   Llit8
+        .quad   Llit16

llvm/test/MC/MachO/AArch64/mergeable.s

@@ -1,4 +1,6 @@
 // RUN: llvm-mc -triple aarch64-apple-darwin14 %s -filetype=obj -o - | llvm-readobj -r --expand-relocs | FileCheck %s
+// FIXME: the final relocation should be internal, but the linker doesn't
+// currently handle the it correctly.
 
 // Test that we "S + K" produce a relocation with a symbol, but just S produces
 // a relocation with the section.
@@ -50,9 +52,9 @@ L1:
 // CHECK-NEXT:       Offset: 0x0
 // CHECK-NEXT:       PCRel: 0
 // CHECK-NEXT:       Length: 3
-// CHECK-NEXT:       Extern: 0
+// CHECK-NEXT:       Extern: 1
 // CHECK-NEXT:       Type: ARM64_RELOC_UNSIGNED (0)
-// CHECK-NEXT:       Symbol: 0x2
+// CHECK-NEXT:       Symbol: L0
 // CHECK-NEXT:       Scattered: 0
 // CHECK-NEXT:     }
 // CHECK-NEXT:   }