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//
// constfold.c
//

#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
//#include <string.h>

#include "slglobals.h"

#if 0
#define DB(X)   X
#else
#define DB(X)
#endif

// IsConstant(expr *)
// return true iff the argument is a constant
static int IsConstant(expr *fexpr)
{
    return fexpr && fexpr->common.kind == CONST_N;
} // IsConstant

// IsConstList(expr *)
// return true iff the argument is a constant or a list of constants
static int IsConstList(expr *fexpr)
{
    while (fexpr &&
           fexpr->common.kind == BINARY_N &&
           fexpr->bin.op == EXPR_LIST_OP
    ) {
        if (!IsConstant(fexpr->bin.left)) return 0;
        if (!(fexpr = fexpr->bin.right)) return 1;
    }
    return fexpr && fexpr->common.kind == CONST_N;
} // IsConstList

// NewConst
// create a new blank constant node we can fill in
// This is a bit of a hack, as the opcode field is really redundant with
// the type info in the node, so we just create an opcode that's as close
// as possible to what we want -- which sometimes may not exist (vectors
// other than float
static expr *NewConst(int base, int len)
{
    float       tmp[4] = { 0, 0, 0, 0 };
    opcode      op = FCONST_OP;

    // This is a bit of a hack -- we use NewFConstNodeV to allocate a node
    // even for non-FCONST_V nodes.  It turns out that it works out ok.
    if (runtime_ops[base]) op = runtime_ops[base]->const_opcode;
    if (len) op++;
    return (expr *)NewFConstNodeV(op, tmp, len, base);
}

// GetConstVal
// get the actual value from a constant node
static scalar_constant *GetConstVal(expr *constexpr) {
    if (!constexpr || constexpr->common.kind != CONST_N) return 0;
    return constexpr->co.val;
} // GetConstVal

typedef struct constlist_iter {
    expr        *curr, *rest;
    int         i, lim;
} constlist_iter;

static void InitConstList_iter(constlist_iter *iter, expr *fexpr)
{
    iter->curr = 0;
    iter->rest = fexpr;
    iter->i = iter->lim = 0;
} // InitConstList_iter

static scalar_constant *ConstListNext(constlist_iter *iter) {
    if (iter->i >= iter->lim) {
        do {
            if (!iter->rest) return 0;
            if (iter->rest->common.kind == BINARY_N &&
                iter->rest->bin.op == EXPR_LIST_OP
            ) {
                iter->curr = iter->rest->bin.left;
                iter->rest = iter->rest->bin.right;
            } else if (iter->rest->common.kind == CONST_N) {
                iter->curr = iter->rest;
                iter->rest = 0;
            } else {
                iter->rest = 0;
                return 0;
            }
        } while (!iter->curr || iter->curr->common.kind != CONST_N);
        iter->i = 0;
        iter->lim = SUBOP_GET_S(iter->curr->co.subop);
    }
    return &iter->curr->co.val[iter->i++];
} // ConstListNext

DB(
static void pconst(scalar_constant *v, int type) {
    switch(type) {
    case TYPE_BASE_BOOLEAN:
        printf("%c", v->i ? 'T' : 'F');
        break;
    case TYPE_BASE_INT:
    case TYPE_BASE_CINT:
        printf("%d", v->i);
        break;
    default:
        printf("%g", v->f);
        break;
    }
}

static void DumpConstList(expr *fexpr, int type) {
    constlist_iter      iter;
    int                 first = 1;
    scalar_constant     *v;

    InitConstList_iter(&iter, fexpr);
    printf("(");
    while ((v = ConstListNext(&iter))) {
        if (first) first = 0;
        else printf(", ");
        pconst(v, type);
    }
    printf(")");
}
)

/*
 * FoldConstants() - Fold this expression if possible.
 *
 */

expr *FoldConstants(expr *fexpr)
{
    return PostApplyToNodes(ConstantFoldNode, fexpr, 0, 0);
}


// ConstantFoldNode
// all the real work is done here
expr *ConstantFoldNode(expr *fexpr, void *_arg1, int arg2)
{
    expr *rv = fexpr;
    int base, target;
    int len;
    int i;
    scalar_constant *a1, *a2;
    void (*unfn)(scalar_constant *, const scalar_constant *) = 0;
    void (*binfn)(scalar_constant *, const scalar_constant *, const scalar_constant *) = 0;
    void (*shfn)(scalar_constant *, const scalar_constant *, int) = 0;
    int (*cmpfn)(const scalar_constant *, const scalar_constant *) = 0;
    int op_offset, a1_mask, a2_mask;
    if (!fexpr) return fexpr;
    switch(fexpr->common.kind) {
    case UNARY_N:
        base = SUBOP_GET_T(fexpr->un.subop);
        len = SUBOP_GET_S(fexpr->un.subop);
        if (fexpr->un.op == VECTOR_V_OP && IsConstList(fexpr->un.arg)) {
            constlist_iter      iter;
            DB (printf("fold VECTOR_V_OP[%d:%d]", len, base);
                DumpConstList(fexpr->un.arg, base);
                printf(" -> ");)
            InitConstList_iter(&iter, fexpr->un.arg);
            rv = NewConst(base, len);
            for (i=0; i<len; i++) {
                rv->co.val[i] = *ConstListNext(&iter);
                DB (if (i) printf(", ");
                    pconst(&rv->co.val[i], base);)
            }
            DB(printf("\n");)
            return rv;
        }
        if (!IsConstant(fexpr->un.arg)) break;
        if (!runtime_ops[base]) break;
        a1 = GetConstVal(fexpr->un.arg);
        switch (fexpr->un.op) {
        case SWIZZLE_Z_OP: {
            int mask = SUBOP_GET_MASK(fexpr->un.subop);
            len = SUBOP_GET_S2(fexpr->un.subop);
            DB (printf("fold SWIZ[%d:%d].", len, base);
                for (i=0; i<len; i++)
                    putchar("xyzw"[(mask>>(i*2))&3]);
                DumpConstList(fexpr->un.arg, base);
                printf(" -> ");)
            rv = NewConst(base, len);
            for (i=0; i==0 || i<len; i++) {
                rv->co.val[i] = a1[mask&3];
                mask >>= 2;
                DB (if (i) printf(", ");
                    pconst(&rv->co.val[i], base);)
            }
            DB(printf("\n");)
            break; }
        case SWIZMAT_Z_OP:
            break;
        case CAST_CS_OP:
        case CAST_CV_OP:
            target = SUBOP_GET_T2(fexpr->un.subop);
            DB (printf("fold CAST[%d:%d->%d]", len, base, target);
                DumpConstList(fexpr->un.arg, base);
                printf(" -> ");)
            unfn = runtime_ops[base]->cvtTo[target];
            if (!unfn && runtime_ops[target])
                unfn = runtime_ops[target]->cvtFrom[base];
            base = target;
            goto normal_unop;
        case CAST_CM_OP:
            break;
        case NEG_OP:
        case NEG_V_OP:
            DB (printf("fold NEG[%d:%d]", len, base);
                DumpConstList(fexpr->un.arg, base);
                printf(" -> ");)
            unfn = runtime_ops[base]->op_neg;
        normal_unop:
            if (!unfn) {
                DB(printf("no function, abort\n");)
                break;
            }
            rv = NewConst(base, len);
            for (i=0; i==0 || i<len; i++) {
                unfn(&rv->co.val[i], &a1[i]);
                DB (if (i) printf(", ");
                    pconst(&rv->co.val[i], base);)
            }
            DB(printf("\n");)
            break;
        case POS_OP:
        case POS_V_OP:
            rv = fexpr->un.arg;
            break;
        case NOT_OP:
        case NOT_V_OP:
            DB (printf("fold NOT[%d:%d]", len, base);
                DumpConstList(fexpr->un.arg, base);
                printf(" -> ");)
            unfn = runtime_ops[base]->op_not;
            goto normal_unop;
        case BNOT_OP:
        case BNOT_V_OP:
            DB (printf("fold BNOT[%d:%d]", len, base);
                DumpConstList(fexpr->un.arg, base);
                printf(" -> ");)
            unfn = runtime_ops[base]->op_bnot;
            goto normal_unop;
            break;
        default:
            break;
        }
        break;
    case BINARY_N:
        if (!IsConstant(fexpr->bin.left) ||
            !IsConstant(fexpr->bin.right)
        )
            break;
        base = SUBOP_GET_T(fexpr->bin.subop);
        if (!runtime_ops[base]) break;
        len = SUBOP_GET_S(fexpr->bin.subop);
        a1 = GetConstVal(fexpr->bin.left);
        a2 = GetConstVal(fexpr->bin.right);
        switch(fexpr->bin.op) {
        case MEMBER_SELECTOR_OP:
        case ARRAY_INDEX_OP:
        case FUN_CALL_OP:
        case FUN_BUILTIN_OP:
        case FUN_ARG_OP:
        case EXPR_LIST_OP:
            break;
        case MUL_OP:
        case MUL_V_OP:
        case MUL_SV_OP:
        case MUL_VS_OP:
            DB (printf("fold MUL");)
            binfn = runtime_ops[base]->op_mul;
            op_offset = fexpr->bin.op - MUL_OP;
        normal_binop:
            DB (printf("[%d:%d]", len, base);
                DumpConstList(fexpr->bin.left, base);
                DumpConstList(fexpr->bin.right, base);
                printf(" -> ");)
            if (!binfn) {
                DB(printf("no function, abort\n");)
                break;
            }
            rv = NewConst(base, len);
            // set a1_mask to all 0s or all 1s, depending on whether a1
            // (left arg) is scalar (all 0s) or vector (all 1s).  a2_mask
            // is set according to a2.  This is dependent on the ordering
            // of the OFFSET_ tags in supprt.h
            a1_mask = 0 - (op_offset&1);
            a2_mask = 0 - (((op_offset>>1)^op_offset)&1);
            for (i=0; i==0 || i<len; i++) {
                binfn(&rv->co.val[i], &a1[i & a1_mask], &a2[i & a2_mask]);
                DB (if (i) printf(", ");
                    pconst(&rv->co.val[i], base);)
            }
            DB(printf("\n");)
            break;
        case DIV_OP:
        case DIV_V_OP:
        case DIV_SV_OP:
        case DIV_VS_OP:
            DB (printf("fold DIV");)
            binfn = runtime_ops[base]->op_div;
            op_offset = fexpr->bin.op - DIV_OP;
            goto normal_binop;
        case MOD_OP:
        case MOD_V_OP:
        case MOD_SV_OP:
        case MOD_VS_OP:
            DB (printf("fold MOD");)
            binfn = runtime_ops[base]->op_mod;
            op_offset = fexpr->bin.op - MOD_OP;
            goto normal_binop;
        case ADD_OP:
        case ADD_V_OP:
        case ADD_SV_OP:
        case ADD_VS_OP:
            DB (printf("fold ADD");)
            binfn = runtime_ops[base]->op_add;
            op_offset = fexpr->bin.op - ADD_OP;
            goto normal_binop;
        case SUB_OP:
        case SUB_V_OP:
        case SUB_SV_OP:
        case SUB_VS_OP:
            DB (printf("fold SUB");)
            binfn = runtime_ops[base]->op_sub;
            op_offset = fexpr->bin.op - SUB_OP;
            goto normal_binop;
        case SHL_OP:
        case SHL_V_OP:
            DB (printf("fold SHL");)
            shfn = runtime_ops[base]->op_shl;
        normal_shiftop:
            DB (printf("[%d:%d]", len, base);
                DumpConstList(fexpr->bin.left, base);
                DumpConstList(fexpr->bin.right, TYPE_BASE_CINT);
                printf(" -> ");)
            if (!shfn) {
                DB(printf("no function, abort\n");)
                break;
            }
            rv = NewConst(base, len);
            for (i=0; i==0 || i<len; i++) {
                shfn(&rv->co.val[i], &a1[i], a2->i);
                DB (if (i) printf(", ");
                    pconst(&rv->co.val[i], base);)
            }
            DB(printf("\n");)
            break;
        case SHR_OP:
        case SHR_V_OP:
            DB (printf("fold SHR");)
            shfn = runtime_ops[base]->op_shr;
            goto normal_shiftop;
        case LT_OP:
        case LT_V_OP:
        case LT_SV_OP:
        case LT_VS_OP:
            DB (printf("fold LT");)
            cmpfn = runtime_ops[base]->op_lt;
            op_offset = fexpr->bin.op - LT_OP;
        normal_cmpop:
            DB (printf("[%d:%d]", len, base);
                DumpConstList(fexpr->bin.left, base);
                DumpConstList(fexpr->bin.right, TYPE_BASE_CINT);
                printf(" -> ");)
            if (!cmpfn) {
                DB(printf("no function, abort\n");)
                break;
            }
            rv = NewConst(TYPE_BASE_BOOLEAN, len);
            // set a1_mask to all 0s or all 1s, depending on whether a1
            // (left arg) is scalar (all 0s) or vector (all 1s).  a2_mask
            // is set according to a2.  This is dependent on the ordering
            // of the OFFSET_ tags in supprt.h
            a1_mask = 0 - (op_offset&1);
            a2_mask = 0 - (((op_offset>>1)^op_offset)&1);
            for (i=0; i==0 || i<len; i++) {
                rv->co.val[i].i = cmpfn(&a1[i & a1_mask], &a2[i & a2_mask]);
                DB (if (i) printf(", ");
                    pconst(&rv->co.val[i], TYPE_BASE_BOOLEAN);)
            }
            DB(printf("\n");)
            break;
        case GT_OP:
        case GT_V_OP:
        case GT_SV_OP:
        case GT_VS_OP:
            cmpfn = runtime_ops[base]->op_gt;
            op_offset = fexpr->bin.op - GT_OP;
            goto normal_cmpop;
        case LE_OP:
        case LE_V_OP:
        case LE_SV_OP:
        case LE_VS_OP:
            cmpfn = runtime_ops[base]->op_le;
            op_offset = fexpr->bin.op - LE_OP;
            goto normal_cmpop;
        case GE_OP:
        case GE_V_OP:
        case GE_SV_OP: