Commit Graph

12 Commits

Author SHA1 Message Date
Rafael Espindola 2658554aec 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
2015-01-19 21:11:14 +00:00
Rafael Espindola 7244bb3c17 Revert "Add r224985 back with two fixes."
This reverts commit r225644 while I debug a regression.

llvm-svn: 226022
2015-01-14 19:07:23 +00:00
Rafael Espindola d9c3e308f5 Add r224985 back with two fixes.
One is that AArch64 has additional restrictions on when local relocations can
be used. We have to take those into consideration when deciding to put a L
symbol in the symbol table or not.

The other is that ld64 requires the relocations to cstring to use linker
visible symbols on AArch64.

Thanks to Michael Zolotukhin for testing this!

Remove doesSectionRequireSymbols.

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: 225644
2015-01-12 18:13:07 +00:00
Lang Hames 04b37c4043 Revert r225048: It broke ObjC on AArch64.
I've filed http://llvm.org/PR22100 to track this issue.

llvm-svn: 225228
2015-01-06 00:54:32 +00:00
Rafael Espindola 54b435ec3c Add r224985 back with a fix.
The issues was that AArch64 has additional restrictions on when local
relocations can be used. We have to take those into consideration when
deciding to put a L symbol in the symbol table or not.

Original message:

Remove doesSectionRequireSymbols.

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: 225048
2014-12-31 17:19:34 +00:00
Rafael Espindola d4da9040de Revert "Remove doesSectionRequireSymbols."
This reverts commit r224985.

I am investigating why it made an Apple bot unhappy.

llvm-svn: 225044
2014-12-31 16:06:48 +00:00
Rafael Espindola b22d5aa49a Remove doesSectionRequireSymbols.
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: 224985
2014-12-30 13:13:27 +00:00
Rafael Espindola 2f471303c1 Simplify test a bit.
It looks like the original intent was to check which symbols were created.
With macho-dump the sections were being checked just to match which symbol
was in which section.

llvm-objdump prints the section a symbol is in.

llvm-svn: 224980
2014-12-30 05:09:17 +00:00
Rafael Espindola 517b47232b Convert test to FileCheck. NFC.
llvm-svn: 224950
2014-12-29 19:50:32 +00:00
Hans Wennborg 1b1a399489 MachObjectWriter: optimize the string table for common suffices
This is a follow-up to r207670 (ELF) and r218636 (COFF).

Differential Revision: http://reviews.llvm.org/D5622

llvm-svn: 219126
2014-10-06 17:05:19 +00:00
Daniel Dunbar 1440fd3539 macho-dump: Fix typo.
llvm-svn: 120185
2010-11-27 04:00:06 +00:00
Daniel Dunbar fe8d866fc7 MC/Mach-O/x86_64: Temporary labels in cstring sections require symbols (and external relocations, but we don't have x86_64 relocations yet).
llvm-svn: 98583
2010-03-15 21:56:50 +00:00