RISC-V ABIs
From Gentoo Wiki
riscv has quite a few ABIs, this page will describe their properties: pointer sizes, compatibility, gcc flags, default linker path.
RISC-V has two integer ABIs and three floating-point ABIs, which can essentially be combined at will. Code generation is controlled by the -mabi argument to compiler calls, which concatenates the integer and floating point ABI name.
Example: -mabi=ilp32d
The choice of ABI places requirements on the instruction set supported by the hardware and emitted by the compiler.
TODO:
Todo:
- add details.
Integer ABIs
ilp32
- int, long, pointers are 32bit
- long long is 64bit
- char is 8bit
- short is 16bit
ilp32 is currently only supported for 32-bit targets.
lp64
- int is 32bit
- long and pointers are 64bit
- long long is 64bit
- char is 8bit
- short is 16bit
lp64 is only supported for 64-bit targets.
Floating Point ABIs
"" (empty string)
- No floating point arguments are passed in registers.
- No requirements on instruction set / hardware.
f
- 32bit and smaller floating point types are passed in registers.
- Requires F type floating point registers and instructions.
d
- 64bit and smaller floating point types are passed in registers.
- Requires D type floating point registers and instructions.