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[lld] macho: Support section branch relocations, including the 1-byte form #169062

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Merged
merged 1 commit into from
Nov 25, 2025
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[lld] macho: Support section branch relocations, including the 1-byte form #169062

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3 changes: 2 additions & 1 deletion lld/MachO/Arch/X86_64.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -54,7 +54,8 @@ static constexpr std::array<RelocAttrs, 10> relocAttrsArray{{
{"UNSIGNED", B(UNSIGNED) | B(ABSOLUTE) | B(EXTERN) | B(LOCAL) | B(BYTE1) |
B(BYTE4) | B(BYTE8)},
{"SIGNED", B(PCREL) | B(EXTERN) | B(LOCAL) | B(BYTE4)},
{"BRANCH", B(PCREL) | B(EXTERN) | B(BRANCH) | B(BYTE1) | B(BYTE4)},
{"BRANCH",
B(PCREL) | B(EXTERN) | B(LOCAL) | B(BRANCH) | B(BYTE1) | B(BYTE4)},
{"GOT_LOAD", B(PCREL) | B(EXTERN) | B(GOT) | B(LOAD) | B(BYTE4)},
{"GOT", B(PCREL) | B(EXTERN) | B(GOT) | B(POINTER) | B(BYTE4)},
{"SUBTRACTOR", B(SUBTRAHEND) | B(EXTERN) | B(BYTE4) | B(BYTE8)},
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4 changes: 2 additions & 2 deletions lld/MachO/InputFiles.cpp
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Expand Up @@ -594,8 +594,8 @@ void ObjFile::parseRelocations(ArrayRef<SectionHeader> sectionHeaders,
// FIXME This logic was written around x86_64 behavior -- ARM64 doesn't
// have pcrel section relocations. We may want to factor this out into
// the arch-specific .cpp file.
assert(target->hasAttr(r.type, RelocAttrBits::BYTE4));
referentOffset = sec.addr + relInfo.r_address + 4 + totalAddend -
referentOffset = sec.addr + relInfo.r_address +
(1ull << relInfo.r_length) + totalAddend -
referentSecHead.addr;
} else {
// The addend for a non-pcrel relocation is its absolute address.
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18 changes: 17 additions & 1 deletion lld/test/MachO/x86-64-relocs.s
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Expand Up @@ -4,6 +4,7 @@
# RUN: llvm-objdump --no-print-imm-hex --section-headers --syms -d %t | FileCheck %s

# CHECK-LABEL: Sections:
# CHECK: __branch_target {{[0-9a-z]+}} [[#%x, BRANCH_SECT:]]
# CHECK: __data {{[0-9a-z]+}} [[#%x, DATA_ADDR:]]

# CHECK-LABEL: SYMBOL TABLE:
Expand All @@ -12,10 +13,18 @@

# CHECK-LABEL: <_main>:
## Test X86_64_RELOC_BRANCH
## Test symbol (extern) relocations first (most common case)
# CHECK: callq 0x[[#%x, F_ADDR]] <_f>
# CHECK: jrcxz 0x[[#%x, F_ADDR]] <_f>
# CHECK: callq 0x[[#%x, G_ADDR]] <_g>
# CHECK: jrcxz 0x[[#%x, G_ADDR]] <_g>
## Test section (local) BRANCH relocations
# CHECK: callq 0x[[#%x, BRANCH_SECT]]
## NOTE: ld64 rejects 1-byte local branch relocations as unsupported, but it
## doesn't take any extra code for us to support it
# CHECK: jrcxz 0x[[#%x, BRANCH_SECT]]

# CHECK-LABEL: <_f>:
## Test extern (symbol) X86_64_RELOC_SIGNED
# CHECK: leaq [[#%u, LOCAL_OFF:]](%rip), %rsi
# CHECK-NEXT: [[#%x, DATA_ADDR - LOCAL_OFF]]
Expand All @@ -33,9 +42,12 @@
_main:
callq _f # X86_64_RELOC_BRANCH with r_length=2
jrcxz _f # X86_64_RELOC_BRANCH with r_length=0
# test negative addends
# Test negative addends
callq _f - 1
jrcxz _f - 1
# Test section relocations
callq L_.branch_target
jrcxz L_.branch_target
mov $0, %rax
ret

Expand All @@ -48,6 +60,10 @@ _f:
movq L_.ptr_1(%rip), %rsi
ret

.section __TEXT,__branch_target
L_.branch_target:
ret

.data
## References to this generate a symbol relocation
_local:
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