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[MC] Support constant offset for symbol PendingFixup 

This patch add support relocation offset of sym+constant(like `foo+4`) form for pending fixup.

In the past, llvm-mc ignored the constant in sym+constant form, for `foo+4`, `4` would be ignored. And test case
```
.text
  ret
  nop
  nop
  .reloc foo+4, R_RISCV_32, 6

.data
.globl foo
foo:
  .word 0
  .word 0
  .word 0
```
when run `llvm-mc -filetype=obj -triple=riscv64 %s | llvm-readobj -r`
The output is
```
Relocations [
  Section (3) .rela.text {
    0x0 R_RISCV_32 - 0x6
  }
]
```

After applying this patch, the output is
```
Relocations [
  Section (3) .rela.text {
    0x4 R_RISCV_32 - 0x6
  }
]
```

Differential Revision: https://reviews.llvm.org/D117316
This commit is contained in:
luxufan 2022-01-14 23:02:27 +08:00
parent cc4beda039
commit d606e23305
2 changed files with 7 additions and 3 deletions
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8
llvm/lib/MC/MCObjectStreamer.cpp
View File

@ -119,7 +119,8 @@ void MCObjectStreamer::resolvePendingFixups() {
continue;
}
flushPendingLabels(PendingFixup.DF, PendingFixup.DF->getContents().size());
PendingFixup.Fixup.setOffset(PendingFixup.Sym->getOffset());
PendingFixup.Fixup.setOffset(PendingFixup.Sym->getOffset() +
PendingFixup.Fixup.getOffset());
// If the location symbol to relocate is in MCEncodedFragmentWithFixups,
// put the Fixup into location symbol's fragment. Otherwise
@ -838,8 +839,9 @@ MCObjectStreamer::emitRelocDirective(const MCExpr &Offset, StringRef Name,
return None;
}
PendingFixups.emplace_back(&SRE.getSymbol(), DF,
MCFixup::create(-1, Expr, Kind, Loc));
PendingFixups.emplace_back(
&SRE.getSymbol(), DF,
MCFixup::create(OffsetVal.getConstant(), Expr, Kind, Loc));
return None;
}

2
llvm/test/MC/RISCV/reloc-directive.s
View File

@ -25,6 +25,7 @@
# CHECK: Section ({{.*}}) .rela.data {
# CHECK-NEXT: 0x0 R_RISCV_32 - 0x6
# CHECK-NEXT: 0x4 R_RISCV_32 - 0x6
# CHECK-NEXT: }
# CHECK: Section ({{.*}}) .rela.debug_line {
@ -55,6 +56,7 @@
.reloc line, R_RISCV_32, 6
.reloc probe, R_RISCV_32, 6
.reloc foo+4, R_RISCV_32, 6
.data
.globl foo
foo: