There are a couple of bugs with the sc, scs, ll, lld instructions expanding:
1. On R6 these instruction pack immediate offset into a 9-bit field. Now
if an immediate exceeds 9-bits assembler does not perform expansion and
just rejects such instruction.
2. On 64-bit non-PIC code if an operand is a symbol assembler generates
incorrect sequence of instructions. It uses R_MIPS_HI16 and R_MIPS_LO16
relocations and skips R_MIPS_HIGHEST and R_MIPS_HIGHER ones.
To solve these problems this patch:
- Introduces `mem_simm9_exp` to mark 9-bit memory immediate operands
which require expansion. Probably later all `mem_simm9` operands will be
able to migrate on `mem_simm9_exp` and we rename it to `mem_simm9`.
- Adds new `OPERAND_MEM_SIMM9` operand type and assigns it to the
`mem_simm9_exp`. That allows to know operand size in the `processInstruction`
method and decide whether we need to expand instruction.
- Adds `expandMem9Inst` method to expand instructions with 9-bit memory
immediate operand. This method just load immediate into a "base"
register used by origibal instruction:
sc $2, 256($sp) => addiu $1, $sp, 256
sc $2, 0($1)
- Fix `expandMem16Inst` to support a correct set of relocations for
symbol loading in case of 64-bit non-PIC code.
ll $12, symbol => lui $12, 0
R_MIPS_HIGHEST symbol
daddiu $12, $12, 0
R_MIPS_HIGHER symbol
dsll $12, $12, 16
daddiu $12, $12, 0
R_MIPS_HI16 symbol
dsll $12, $12, 16
ll $12, 0($12)
R_MIPS_LO16 symbol
- Fix `expandMem16Inst` to unify handling of 3 and 4 operands
instructions.
- Delete unused now `MipsTargetStreamer::emitSCWithSymOffset` method.
Task for next patches - implement expanding for other instructions use
`mem_simm9` operand and other `mem_simm##` operands.
Differential Revision: https://reviews.llvm.org/D70648
Simon Atanasyan