Merge pull request riscv-non-isa#67 from kito-cheng/riscv_vector_cc

Function attribute for standard vector calling convention variant: riscv_vector_cc

Author: kito-cheng

riscv-c-api.md

@@ -305,6 +305,19 @@ __attribute__((target("arch=+v"))) int foo(void) { return 0; }
 __attribute__((target("arch=+zbb"))) int foo(void) { return 1; }
 ```
 
+### riscv_vector_cc
+
+Supported Syntaxes:
+| Style  | Syntax                              |
+| ------ | ----------------------------------- |
+| GNU    | `__attribute__((riscv_vector_cc)))` |
+| C++11  | `[[riscv::vector_cc]]`              |
+| C23    | `[[riscv::vector_cc]]`              |
+
+Functions declared with this attribute will use to the standard vector calling
+convention variant as defined in the RISC-V psABI, even if the function has
+vector arguments or a return value.
+
 ## Intrinsic Functions
 
 Intrinsic functions (or intrinsics or built-ins) are expanded into instruction sequences by compilers.