Assemblers change certain relocations referencing a local symbol to
reference the section symbol instead. This conversion is disabled for
many conditions (`shouldRelocateWithSymbol`), e.g. TLS symbol, for most
targets (including AArch32, x86, PowerPC, and RISC-V) GOT-generating
relocations.
However, AArch64 encodes the GOT-generating intent in MCValue::RefKind
instead of MCSymbolRef::Kind (see commit
0999cbd0b9ed8aa893cce10d681dec6d54b200ad (2014)), therefore not affected
by the code `case MCSymbolRefExpr::VK_GOT:`. As GNU ld and ld.lld
create GOT entries based on the symbol, ignoring addend, the two ldr
instructions will share the same GOT entry, which is not expected:
```
ldr x1, [x1, :got_lo12:x] // converted to .data+0
ldr x1, [x1, :got_lo12:y] // converted to .data+4
.data
// .globl x, y would suppress STT_SECTION conversion
x:
.zero 4
y:
.long 42
```
This patch changes AArch64 to suppress local symbol to STT_SECTION
conversion for GOT relocations, matching most other targets. x and y
will use different GOT entries, which IMO is the most sensable behavior.
With this change, the ABI decision on https://github.com/ARM-software/abi-aa/issues/217
will only affect relocations explicitly referencing STT_SECTION symbols, e.g.
```
ldr x1, [x1, :got_lo12:(.data+0)]
ldr x1, [x1, :got_lo12:(.data+4)]
// I consider this unreasonable uses
```
IMO all reasonable use cases are unaffected.
Link: https://github.com/llvm/llvm-project/issues/63418
GNU assembler PR: https://sourceware.org/bugzilla/show_bug.cgi?id=30788
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D158577
Change to use Ctx.reportError() instead of llvm_unreachable for
better error handling. Also correct evaluateAsRelocatableImpl().
Reviewed By: simoll
Differential Revision: https://reviews.llvm.org/D115251
Change to use R_VE_SREL32 for relative branch instructions instead of
R_VE_PC_LO32 in order to check ranges of relative branch isntructions
at link time correctly.
Reviewed By: simoll
Differential Revision: https://reviews.llvm.org/D115097
Summary:
Change VEAsmParser to support identification with relocation information
in assmebler. Change VEAsmBackend to support relocation information in
MC layer. Change VEDisassembler and VEMCCodeEmitter to support binary
generation of branch target operands. Add REFLONG fixup and variant kind
to support new R_VE_REFLONG ELF symbol. And, add regression test in both
MC and CodeGen to check binary genaration with relocation information.
Differential Revision: https://reviews.llvm.org/D81553
Summary:
This patch includes following items.
- Adds AsmParser and minimum AsmBackend/ELFObjectWriter/MCCodeEmitter to
support only LEA instruction in order to reduce the size of this patch.
- Adds regression test of MC layer for a LEA instruction.
- Relocations are not supported this time to reduce the size of this patch.
Differential Revision: https://reviews.llvm.org/D79546
