[Libre-soc-bugs] [Bug 980] Implement C-based Power ISA pseudocode compiler

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=980

--- Comment #98 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Dmitry Selyutin from comment #95)
> What's the point of having ok or flags in each and every integer?

mostly because that's how we did it in python...yeah I can see your point why
we shouldn't do it that way.

how about:

#include <stdbool.h> // so we can use bool regardless of C or C++
#include <stdint.h>

typedef enum oppc_type_tag {
    oppc_tt_sel_int,
    // add more stuff later
} oppc_type_tag;

typedef struct oppc_sel_int {
    uint32_t bits;
    union {
        uint64_t small; // for bits <= 64
        // add another field later for > 64 bits
    };
} oppc_sel_int;

typedef struct oppc_value {
    oppc_type_tag type : 4;
    bool ok : 1;
    : 0; // terminate bitfield
    union {
        oppc_sel_int si;
        // add more stuff later
    };
} oppc_value;

static inline oppc_value oppc_si_small(uint64_t value, uint32_t bits) {
    assert(bits <= 64);
    if(bits < 64)
        // note ULL is guaranteed to be >= 64-bits so this works.
        value &= (1ULL << bits) - 1ULL;
    return (oppc_value){
        .type = oppc_tt_sel_int,
        .ok = true,
        .si = {.bits = bits, .small = value},
    };
}

static inline oppc_value oppc_add(oppc_value a, oppc_value b) {
    assert(a.type == oppc_tt_si);
    assert(b.type == oppc_tt_si);
    assert(a.si.bits == b.si.bits);
    assert(a.si.bits <= 64);
    return oppc_si_small(a.si.small + b.si.small, a.si.bits);
}

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