Modifies RISC-V specific assembler options inline with the assembly code.
This is used when particular instruction sequences must be assembled with a
specific set of options. For example, since we relax addressing sequences to
shorter GP-relative sequences when possible the initial load of GP must not be
relaxed and should be emitted as something like
.option push
.option norelax
la gp, __global_pointer$
.option pop
in order to produce after linker relaxation the expected
auipc gp, %pcrel_hi(__global_pointer$)
addi gp, gp, %pcrel_lo(__global_pointer$)
instead of just
addi gp, gp, 0
It's not expected that options are changed in this manner during regular use,
but there are a handful of esoteric cases like the one above where users need
to disable particular features of the assembler for particular code sequences.
The complete list of option arguments is shown below:
push
pop
- Pushes or pops the current option stack. These should be used whenever
changing an option in line with assembly code in order to ensure the user's
command-line options are respected for the bulk of the file being assembled.
rvc
norvc
- Enables or disables the generation of compressed instructions. Instructions
are opportunistically compressed by the RISC-V assembler when possible, but
sometimes this behavior is not desirable.
pic
nopic
- Enables or disables position-independent code generation. Unless you really
know what you're doing, this should only be at the top of a file.
relax
norelax
- Enables or disables relaxation. The RISC-V assembler and linker
opportunistically relax some code sequences, but sometimes this behavior is not
desirable.