Add r224985 back with fixes.

The fixes are to note that AArch64 has additional restrictions on when local
relocations can be used. In particular, ld64 requires that relocations to
cstring/cfstrings use linker visible symbols.

Original message:

In an assembly expression like

bar:
  .long L0 + 1

the intended semantics is that bar will contain a pointer one byte past L0.

In sections that are merged by content (strings, 4 byte constants, etc), a
single position in the section doesn't give the linker enough information.
For example, it would not be able to tell a relocation must point to the
end of a string, since that would look just like the start of the next.

The solution used in ELF to use relocation with symbols if there is a non-zero
addend.

In MachO before this patch we would just keep all symbols in some sections.

This would miss some cases (only cstrings on x86_64 were implemented) and was
inefficient since most relocations have an addend of 0 and can be represented
without the symbol.

This patch implements the non-zero addend logic for MachO too.

llvm-svn: 226503

1 files changed, 1 insertions, 16 deletions

diff --git a/llvm/lib/MC/MCAsmInfoDarwin.cpp b/llvm/lib/MC/MCAsmInfoDarwin.cpp
index 04cc0ff4a86..f7054902f24 100644
--- a/llvm/lib/MC/MCAsmInfoDarwin.cpp
+++ b/llvm/lib/MC/MCAsmInfoDarwin.cpp
@@ -27,22 +27,7 @@ bool MCAsmInfoDarwin::isSectionAtomizableBySymbols(
   // contain.
   // Sections holding 2 byte strings require symbols in order to be atomized.
   // There is no dedicated section for 4 byte strings.
-  if (SMO.getKind().isMergeable1ByteCString())
-    return false;
-
-  if (SMO.getSegmentName() == "__TEXT" &&
-      SMO.getSectionName() == "__objc_classname" &&
-      SMO.getType() == MachO::S_CSTRING_LITERALS)
-    return false;
-
-  if (SMO.getSegmentName() == "__TEXT" &&
-      SMO.getSectionName() == "__objc_methname" &&
-      SMO.getType() == MachO::S_CSTRING_LITERALS)
-    return false;
-
-  if (SMO.getSegmentName() == "__TEXT" &&
-      SMO.getSectionName() == "__objc_methtype" &&
-      SMO.getType() == MachO::S_CSTRING_LITERALS)
+  if (SMO.getType() == MachO::S_CSTRING_LITERALS)
     return false;
 
   if (SMO.getSegmentName() == "__DATA" && SMO.getSectionName() == "__cfstring")