RISC-V: Add riscv_vector_cc function attribute

Standard vector calling convention variant will only enabled when function
has vector argument or returning value by default, however user may also
want to invoke function without that during a vectorized loop at some situation,
but it will cause a huge performance penalty due to vector register store/restore.

So user can declare function with this riscv_vector_cc attribute like below, that could enforce
function will use standard vector calling convention variant.

void foo() __attribute__((riscv_vector_cc));
[[riscv::vector_cc]] void foo(); // For C++11 and C23

For more details please reference the below link.
https://github.com/riscv-non-isa/riscv-c-api-doc/pull/67

gcc/ChangeLog:

	* config/riscv/riscv.cc (TARGET_GNU_ATTRIBUTES): Add riscv_vector_cc
	attribute to riscv_attribute_table.
	(riscv_vector_cc_function_p): Return true if FUNC is a riscv_vector_cc function.
	(riscv_fntype_abi): Add riscv_vector_cc attribute check.
	* doc/extend.texi: Add riscv_vector_cc attribute description.

gcc/testsuite/ChangeLog:

	* g++.target/riscv/rvv/base/attribute-riscv_vector_cc-error.C: New test.
	* gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-callee-saved.c: New test.
	* gcc.target/riscv/rvv/base/attribute-riscv_vector_cc-error.c: New test.

0 files changed, 0 insertions, 0 deletions