llvm-6502/test/MC/MachO
Peter Collingbourne c39f5dd0e2 MC: For variable symbols, maintain MCSymbol::Section as a cache.
Fixes PR19582.

Previously, when an asm assignment (.set or =) was created, we would look up
the section immediately in MCSymbol::setVariableValue. This caused symbols
to receive the wrong section if the RHS of the assignment had not been seen
yet. This had a knock-on effect in the object file emitters, causing them
to emit extra symbols, or to give symbols the wrong visibility or the wrong
section. For example, in the following asm:

.data
.Llocal:

.text
leaq .Llocal1(%rip), %rdi
.Llocal1 = .Llocal2
.Llocal2 = .Llocal

the first assignment would give .Llocal1 a null section, which would never get
fixed up by the second assignment. This would cause the ELF object file emitter
to consider .Llocal1 to be an undefined symbol and give it external linkage,
even though .Llocal1 should not have been emitted at all in the object file.

Or in the following asm:

alias_to_local = Ltmp0
Ltmp0:

the Mach-O object file emitter would give the alias_to_local symbol a n_type
of N_SECT and a n_sect of 0.  This is invalid under the Mach-O specification,
which requires N_SECT symbols to receive a non-zero section number if the
symbol is defined in a section in the object file.

https://developer.apple.com/library/mac/documentation/DeveloperTools/Conceptual/MachORuntime/#//apple_ref/c/tag/nlist

After this change we do not look up the section when the assignment is created,
but instead look it up on demand and store it in Section, which is treated
as a cache if the symbol is a variable symbol.

This change also fixes a bug in MCExpr::FindAssociatedSection. Previously,
if we saw a subtraction, we would return the first referenced section, even in
cases where we should have been returning the absolute pseudo-section. Now we
always return the absolute pseudo-section for expressions that subtract two
section-derived expressions. This isn't always correct (e.g. if one of the
sections ends up being laid out at an absolute address), but it's probably
the best we can do without more context.

This allows us to remove code in two places where we appear to have been
working around this bug, in MachObjectWriter::markAbsoluteVariableSymbols
and in X86AsmPrinter::EmitStartOfAsmFile.

Re-applies r233595 (aka D8586), which was reverted in r233898.

Differential Revision: http://reviews.llvm.org/D8798

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233995 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-03 01:46:11 +00:00
..
AArch64 [opaque pointer type] Add textual IR support for explicit type parameter to gep operator 2015-03-13 18:20:45 +00:00
ARM MC: For variable symbols, maintain MCSymbol::Section as a cache. 2015-04-03 01:46:11 +00:00
absolute.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
absolutize.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
bad-darwin-x86_64-32-bit-abs-addr.s
bad-darwin-x86_64-diff-relocs.s
bad-darwin-x86_64-reloc-expr1.s Fix a Mach-O assembler segfault for a subtraction expression with an undefined symbol. 2014-10-24 22:39:40 +00:00
bad-darwin-x86_64-reloc-expr2.s Fix a Mach-O assembler segfault for a subtraction expression with an undefined symbol. 2014-10-24 22:39:40 +00:00
bad-darwin-x86_64-reloc-expr.s Fix the assembler to print a better relocatable expression error 2014-04-22 17:27:29 +00:00
bad-dollar.s
bad-indirect-symbols.s
bad-macro.s
bss.s Fix known typos 2014-01-24 17:20:08 +00:00
comm-1.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
cstexpr-gotpcrel-32.ll [opaque pointer type] Add textual IR support for explicit type parameter to gep operator 2015-03-13 18:20:45 +00:00
cstexpr-gotpcrel-64.ll [AsmPrinter] Don't assert on GOT equivalent non-constant users. 2015-03-27 01:40:54 +00:00
darwin-complex-difference.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
darwin-x86_64-diff-reloc-assign-2.s Don't produce relocations for a difference in a section with no symbols. 2014-11-04 22:10:33 +00:00
darwin-x86_64-diff-reloc-assign.s
darwin-x86_64-diff-relocs.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
darwin-x86_64-nobase-relocs.s
darwin-x86_64-reloc-offsets.s
darwin-x86_64-reloc.s Convert test to llvm-readobj. NFC. 2014-12-26 22:47:39 +00:00
data.s
debug_frame.s [MC] Emit an error if cfi_startproc is used before a symbol is defined. 2014-04-15 01:17:45 +00:00
diff-with-two-sections.s
direction_labels.s
eh_symbol.s Change the default input for llvm-nm to be a.out instead of standard input 2014-06-23 20:27:53 +00:00
eh-frame-reloc.s X86: drop relocations on __eh_frame sections globally. 2014-07-22 15:47:09 +00:00
file.s Drop support for an old version of ld64 (from darwin 9). 2014-10-21 18:31:09 +00:00
gen-dwarf-cpp.s llvm/test/MC/MachO/gen-dwarf-cpp.s: Relax an expression to match DOS pat. 2014-03-17 05:31:54 +00:00
gen-dwarf-macro-cpp.s
gen-dwarf-producer.s
gen-dwarf.s [dwarfdump] Dump full filenames as DW_AT_(decl|call)_file attribute values 2014-09-22 12:36:04 +00:00
i386-large-relocations.s
indirect-symbols.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
jcc.s
lcomm-attributes.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
linker-option-1.s
linker-option-2.s
linker-options.ll IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
lit.local.cfg Reduce verbiage of lit.local.cfg files 2014-06-09 22:42:55 +00:00
loc.s
osx-version-min-load-command.s Adds the next bit of support for llvm-objdump’s -private-headers for executable Mach-O files. 2014-09-04 16:54:47 +00:00
pcrel-to-other-section.s
pr19185.s Always use a temp symbol for CIE. 2014-06-20 23:54:32 +00:00
previous.s
pushsection.s
relax-jumps.s
relax-recompute-align.s
reloc-diff.s
reloc-pcrel-offset.s
reloc-pcrel.s
reloc.s Use llvm-readobj. NFC. 2014-12-26 18:22:05 +00:00
section-align-1.s
section-align-2.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
section-attributes.s
section-flags.s
string-table.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
symbol-diff.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
symbol-flags.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
symbol-indirect.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
symbols-1.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
tbss.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
tdata.s
temp-labels.s This command line option is only used in one place. Move it there and 2014-05-21 00:20:01 +00:00
thread_init_func.s
tls.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
tlv-bss.ll [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
tlv-reloc.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
tlv.s
values.s
variable-errors.s
variable-exprs.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
weakdef.s
x86_32-optimal_nop.s
x86_32-scattered-reloc-fallback.s
x86_32-sections.s
x86_32-symbols.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
x86_64-mergeable.s Add r224985 back with fixes. 2015-01-19 21:11:14 +00:00
x86_64-reloc-arithmetic.s
x86_64-sections.s
x86_64-symbols.s Add r224985 back with fixes. 2015-01-19 21:11:14 +00:00
x86-data-in-code.ll [opaque pointer type] Add textual IR support for explicit type parameter to load instruction 2015-02-27 21:17:42 +00:00
zerofill-1.s
zerofill-2.s
zerofill-3.s MachObjectWriter: optimize the string table for common suffices 2014-10-06 17:05:19 +00:00
zerofill-4.s
zerofill-5.s
zerofill-sect-align.s