k: A memory operand whose address is formed by a base register and
(optionally scaled) index register.
m: A memory operand whose address is formed by a base register and
offset that is suitable for use in instructions with the same
addressing mode as st.w and ld.w.
ZB: An address that is held in a general-purpose register. The offset
is zero.
ZC: A memory operand whose address is formed by a base register and
offset that is suitable for use in instructions with the same
addressing mode as ll.w and sc.w.
Differential Revision: https://reviews.llvm.org/D134638
Reuse most of RISCV's implementation with several exceptions:
1. Assign signext/zeroext attribute to args passed in stack.
On RISCV, integer scalars passed in registers have signext/zeroext
when promoted, but are anyext if passed on the stack. This is defined
in early RISCV ABI specification. But after this change [1], integers
should also be signext/zeroext if passed on the stack. So I think
RISCV's ABI lowering should be updated [2].
While in LoongArch ABI spec, we can see that integer scalars narrower
than GRLEN bits are zero/sign-extended no matter passed in registers
or on the stack.
2. Zero-width bit fields are ignored.
This matches GCC's behavior but it hasn't been documented in ABI sepc.
See https://gcc.gnu.org/r12-8294.
3. `char` is signed by default.
There is another difference worth mentioning is that `char` is signed
by default on LoongArch while it is unsigned on RISCV.
This patch also adds `_BitInt` type support to LoongArch and handle it
in LoongArchABIInfo::classifyArgumentType.
[1] cec39a064e
[2] https://github.com/llvm/llvm-project/issues/57261
Differential Revision: https://reviews.llvm.org/D132285
With the initial support added, clang can compile `helloworld` C
to executable file for loongarch64. For example:
```
$ cat hello.c
int main() {
printf("Hello, world!\n");
return 0;
}
$ clang --target=loongarch64-unknown-linux-gnu --gcc-toolchain=xxx --sysroot=xxx hello.c
```
The output a.out can run within qemu or native machine. For example:
```
$ file ./a.out
./a.out: ELF 64-bit LSB pie executable, LoongArch, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-loongarch-lp64d.so.1, for GNU/Linux 5.19.0, with debug_info, not stripped
$ ./a.out
Hello, world!
```
Currently gcc toolchain and sysroot can be found here:
https://github.com/loongson/build-tools/releases/download/2022.08.11/loongarch64-clfs-5.1-cross-tools-gcc-glibc.tar.xz
Reference: https://github.com/loongson/LoongArch-Documentation
The last commit hash (main branch) is:
99016636af64d02dee05e39974d4c1e55875c45b
Note loongarch32 is not fully tested because there is no reference
gcc toolchain yet.
Differential Revision: https://reviews.llvm.org/D130255
Fangrui Song