Rename overloaded intrinsics

[HanKuanChen]

I notice the overloaded intrinsic function name is very unfriendly to C++ template.
For example, if we want to do element-wise max for two array, we will write

#include <riscv_vector.h>

vint32m8_t vle_m8(const int32_t *ptr, size_t vl)
{
    return vle32_v_i32m8(ptr, vl);
}

vint32m8_t max(const int32_t *lhs, const int32_t *rhs, size_t vl)
{
    return vmax(vle_m8(lhs, vl), vle_m8(rhs, vl), vl);
}

To make it support unsigned and float, we will write

#include <riscv_vector.h>

vint32m8_t vle_m8(const int32_t *ptr, size_t vl)
{
    return vle32_v_i32m8(ptr, vl);
}

vint32m8_t max(const int32_t *lhs, const int32_t *rhs, size_t vl)
{
    return vmax(vle_m8(lhs, vl), vle_m8(rhs, vl), vl);
}

vuint32m8_t vle_m8(const uint32_t *ptr, size_t vl)
{
    return vle32_v_u32m8(ptr, vl);
}

vuint32m8_t max(const uint32_t *lhs, const uint32_t *rhs, size_t vl)
{
    return vmaxu(vle_m8(lhs, vl), vle_m8(rhs, vl), vl);
}

vfloat32m8_t vle_m8(const float *ptr, size_t vl)
{
    return vle32_v_f32m8(ptr, vl);
}

vfloat32m8_t max(const float *lhs, const float *rhs, size_t vl)
{
    return vfmax(vle_m8(lhs, vl), vle_m8(rhs, vl), vl);
}

However, they cannot write in a simple C++ template, since max has different name (vmax, vmaxu, vfmax).

#include <riscv_vector.h>

vint32m8_t vle_m8(const int32_t *ptr, size_t vl)
{
    return vle32_v_i32m8(ptr, vl);
}

vuint32m8_t vle_m8(const uint32_t *ptr, size_t vl)
{
    return vle32_v_u32m8(ptr, vl);
}

vfloat32m8_t vle_m8(const float *ptr, size_t vl)
{
    return vle32_v_f32m8(ptr, vl);
}

template<class T>
auto max(T lhs, T rhs, size_t vl)
{
    // return vmax(vle_m8(lhs, vl), vle_m8(rhs, vl), vl); // only valid for signed
    // return vmaxu(vle_m8(lhs, vl), vle_m8(rhs, vl), vl); // only valid for unsigned
    // return vfmax(vle_m8(lhs, vl), vle_m8(rhs, vl), vl); // only valid for float
}

We should make intrinsics have same name if they have same semantic.
For example,
vadd, vfadd -> vadd
vwadd, vfwadd -> vwadd
vmax, vmaxu, vfmax -> vmax
vmseq, vmfeq -> vmseq
vredsum, vfredusum -> vredsum

Old intrinsics will be kept (backward compatibility).

[Hsiangkai]

I am not sure if we should provide such intrinsics for C++ template. In the previous discussion #7, we decide to provide 1-to-1 intrinsics. Is it possible to provide wrapper functions in users' code to meet the purpose?

[HanKuanChen]

1. If users want to use 1-to-1 intrinsic, they can use intrinsics which is in intrinsic_funcs.md. What I want to rename is only overloaded intrinsics, which is an optional implementation for compiler.
2. The amount of riscv vector type is huge, this would be a huge effort for users to do this. Meanwhile, if users want to use C++ template, all of them will face the same problem.

[Hsiangkai]

It may make sense to define them in the overloaded interface. Wait for others' opinions.

[kito-cheng]

+1 from me.

[eopXD]

This is a good feature to have. Let's revisit this after the v1.0 release?

[sh1boot]

The __riscv_vleXX_v_SXXmY() situation, where the element type can be deduced even while LMUL cannot, also exists for __riscv_vget() and __riscv_vlmul_ext() and __riscv_vlmul_trunc().

Conversely, __riscv_vreinterpret() can deduce LMUL since it's not legal to change it using reinterpret anyway.

These all become a nightmare as soon as people start using typedef under conditional compilation and then having to map all the intrinsic operations through at the same time.