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[lld/mac] Fix alignment on subsections

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On a section with alignment of 16, subsections aligned to 16-byte
boundaries should keep their 16-byte alignment.

Fixes PR50274. (The same bug could have happened with -order_file
previously.)

Differential Revision: https://reviews.llvm.org/D102139
This commit is contained in:
Nico Weber
2021-05-09 18:35:16 -04:00
parent 0f8854f7f5
commit 7f673fcaa9
2 changed files with 68 additions and 1 deletions
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3
lld/MachO/InputFiles.cpp
View File

@@ -580,6 +580,7 @@ void ObjFile::parseSymbols(ArrayRef<typename LP::section> sectionHeaders,
return nList[lhs].n_value < nList[rhs].n_value;
});
uint64_t sectionAddr = sectionHeaders[i].addr;
uint32_t sectionAlign = 1u << sectionHeaders[i].align;
// We populate subsecMap by repeatedly splitting the last (highest address)
// subsection.
@@ -622,7 +623,7 @@ void ObjFile::parseSymbols(ArrayRef<typename LP::section> sectionHeaders,
// TODO: ld64 appears to preserve the original alignment as well as each
// subsection's offset from the last aligned address. We should consider
// emulating that behavior.
nextIsec->align = MinAlign(isec->align, sym.n_value);
nextIsec->align = MinAlign(sectionAlign, sym.n_value);
subsecMap.push_back({sym.n_value - sectionAddr, nextIsec});
subsecEntry = subsecMap.back();
}

66
lld/test/MachO/weak-definition-gc.s
View File

@@ -53,6 +53,19 @@
# RUN: %lld -dylib -o %t/out.dylib %t/weak-sub-alt.o %t/weak-sub-alt2.o
# RUN: %lld -dylib -o %t/out.dylib %t/weak-sub-alt2.o %t/weak-sub-alt.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin19.0.0 %t/weak-aligned-1.s -o %t/weak-aligned-1.o
# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin19.0.0 %t/weak-aligned-2.s -o %t/weak-aligned-2.o
# RUN: %lld -o %t/out -lSystem %t/weak-aligned-1.o %t/weak-aligned-2.o
# RUN: llvm-objdump --syms --section=__const --full-contents %t/out | FileCheck --check-prefix=ALIGN %s
# ALIGN: SYMBOL TABLE:
# ALIGN-DAG: [[#%x, ADDR:]] l O __DATA_CONST,__const _weak1
# ALIGN-DAG: {{0*}}[[#ADDR+ 0x4]] l O __DATA_CONST,__const _weak3
# ALIGN-DAG: {{0*}}[[#ADDR+ 0x8]] l O __DATA_CONST,__const _weak2
# ALIGN-DAG: {{0*}}[[#ADDR+0x10]] g O __DATA_CONST,__const _aligned
# ALIGN: Contents of section __DATA_CONST,__const:
# ALIGN-NEXT: {{0*}}[[#ADDR]] 11111111 33333333 22222222 00000000
# ALIGN-NEXT: {{0*}}[[#ADDR+0x10]] 81818181 81818181 82828282 82828282
#--- weak-sub.s
.globl _foo, _bar
.weak_definition _foo, _bar
@@ -129,3 +142,56 @@ _ref:
callq _bar
.subsections_via_symbols
#--- weak-aligned-1.s
.section __DATA,__const
.p2align 3
.globl _weak1
.weak_def_can_be_hidden _weak1
_weak1:
.4byte 0x11111111
.globl _weak3
.weak_def_can_be_hidden _weak3
_weak3:
.4byte 0x33333333
.subsections_via_symbols
#--- weak-aligned-2.s
# _weak1 and _weak3 are already in weak-aligned-1,
# so from _weak1-3 in this file only _weak2 is used.
# However, _aligned still has to stay aligned to a 16-byte boundary.
.section __DATA,__const
.p2align 3
.globl _weak1
.weak_def_can_be_hidden _weak1
_weak1:
.4byte 0x11111111
.globl _weak2
.weak_def_can_be_hidden _weak2
_weak2:
.4byte 0x22222222
.globl _weak3
.weak_def_can_be_hidden _weak3
_weak3:
.4byte 0x33333333
.section __DATA,__const
.p2align 4
.globl _aligned
_aligned:
.8byte 0x8181818181818181
.8byte 0x8282828282828282
.section __TEXT,__text
.globl _main
_main:
movl _weak1(%rip), %eax
movl _weak2(%rip), %ebx
movaps _aligned(%rip), %xmm0
retq
.subsections_via_symbols