turnip: implement VK_EXT_4444_formats

[mesa.git] / src / freedreno / ir3 / ir3_ra.c

/*
 * Copyright (C) 2014 Rob Clark <robclark@freedesktop.org>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * Authors:
 *    Rob Clark <robclark@freedesktop.org>
 */

#include "util/u_math.h"
#include "util/register_allocate.h"
#include "util/ralloc.h"
#include "util/bitset.h"

#include "ir3.h"
#include "ir3_shader.h"
#include "ir3_ra.h"


#ifdef DEBUG
#define RA_DEBUG (ir3_shader_debug & IR3_DBG_RAMSGS)
#else
#define RA_DEBUG 0
#endif
#define d(fmt, ...) do { if (RA_DEBUG) { \
        printf("RA: "fmt"\n", ##__VA_ARGS__); \
} } while (0)

#define di(instr, fmt, ...) do { if (RA_DEBUG) { \
        printf("RA: "fmt": ", ##__VA_ARGS__); \
        ir3_print_instr(instr); \
} } while (0)

/*
 * Register Assignment:
 *
 * Uses the register_allocate util, which implements graph coloring
 * algo with interference classes.  To handle the cases where we need
 * consecutive registers (for example, texture sample instructions),
 * we model these as larger (double/quad/etc) registers which conflict
 * with the corresponding registers in other classes.
 *
 * Additionally we create additional classes for half-regs, which
 * do not conflict with the full-reg classes.  We do need at least
 * sizes 1-4 (to deal w/ texture sample instructions output to half-
 * reg).  At the moment we don't create the higher order half-reg
 * classes as half-reg frequently does not have enough precision
 * for texture coords at higher resolutions.
 *
 * There are some additional cases that we need to handle specially,
 * as the graph coloring algo doesn't understand "partial writes".
 * For example, a sequence like:
 *
 *   add r0.z, ...
 *   sam (f32)(xy)r0.x, ...
 *   ...
 *   sam (f32)(xyzw)r0.w, r0.x, ...  ; 3d texture, so r0.xyz are coord
 *
 * In this scenario, we treat r0.xyz as class size 3, which is written
 * (from a use/def perspective) at the 'add' instruction and ignore the
 * subsequent partial writes to r0.xy.  So the 'add r0.z, ...' is the
 * defining instruction, as it is the first to partially write r0.xyz.
 *
 * To address the fragmentation that this can potentially cause, a
 * two pass register allocation is used.  After the first pass the
 * assignment of scalars is discarded, but the assignment of vecN (for
 * N > 1) is used to pre-color in the second pass, which considers
 * only scalars.
 *
 * Arrays of arbitrary size are handled via pre-coloring a consecutive
 * sequence of registers.  Additional scalar (single component) reg
 * names are allocated starting at ctx->class_base[total_class_count]
 * (see arr->base), which are pre-colored.  In the use/def graph direct
 * access is treated as a single element use/def, and indirect access
 * is treated as use or def of all array elements.  (Only the first
 * def is tracked, in case of multiple indirect writes, etc.)
 *
 * TODO arrays that fit in one of the pre-defined class sizes should
 * not need to be pre-colored, but instead could be given a normal
 * vreg name.  (Ignoring this for now since it is a good way to work
 * out the kinks with arbitrary sized arrays.)
 *
 * TODO might be easier for debugging to split this into two passes,
 * the first assigning vreg names in a way that we could ir3_print()
 * the result.
 */


static struct ir3_instruction * name_to_instr(struct ir3_ra_ctx *ctx, unsigned name);

static bool name_is_array(struct ir3_ra_ctx *ctx, unsigned name);
static struct ir3_array * name_to_array(struct ir3_ra_ctx *ctx, unsigned name);

/* does it conflict? */
static inline bool
intersects(unsigned a_start, unsigned a_end, unsigned b_start, unsigned b_end)
{
        return !((a_start >= b_end) || (b_start >= a_end));
}

static bool
instr_before(struct ir3_instruction *a, struct ir3_instruction *b)
{
        if (a->flags & IR3_INSTR_UNUSED)
                return false;
        return (a->ip < b->ip);
}

static struct ir3_instruction *
get_definer(struct ir3_ra_ctx *ctx, struct ir3_instruction *instr,
                int *sz, int *off)
{
        struct ir3_ra_instr_data *id = &ctx->instrd[instr->ip];
        struct ir3_instruction *d = NULL;

        if (ctx->scalar_pass) {
                id->defn = instr;
                id->off = 0;
                id->sz = 1;     /* considering things as N scalar regs now */
        }

        if (id->defn) {
                *sz = id->sz;
                *off = id->off;
                return id->defn;
        }

        if (instr->opc == OPC_META_COLLECT) {
                /* What about the case where collect is subset of array, we
                 * need to find the distance between where actual array starts
                 * and collect..  that probably doesn't happen currently.
                 */
                int dsz, doff;

                /* note: don't use foreach_ssa_src as this gets called once
                 * while assigning regs (which clears SSA flag)
                 */
                foreach_src_n (src, n, instr) {
                        struct ir3_instruction *dd;
                        if (!src->instr)
                                continue;

                        dd = get_definer(ctx, src->instr, &dsz, &doff);

                        if ((!d) || instr_before(dd, d)) {
                                d = dd;
                                *sz = dsz;
                                *off = doff - n;
                        }
                }

        } else if (instr->cp.right || instr->cp.left) {
                /* covers also the meta:fo case, which ends up w/ single
                 * scalar instructions for each component:
                 */
                struct ir3_instruction *f = ir3_neighbor_first(instr);

                /* by definition, the entire sequence forms one linked list
                 * of single scalar register nodes (even if some of them may
                 * be splits from a texture sample (for example) instr.  We
                 * just need to walk the list finding the first element of
                 * the group defined (lowest ip)
                 */
                int cnt = 0;

                /* need to skip over unused in the group: */
                while (f && (f->flags & IR3_INSTR_UNUSED)) {
                        f = f->cp.right;
                        cnt++;
                }

                while (f) {
                        if ((!d) || instr_before(f, d))
                                d = f;
                        if (f == instr)
                                *off = cnt;
                        f = f->cp.right;
                        cnt++;
                }

                *sz = cnt;

        } else {
                /* second case is looking directly at the instruction which
                 * produces multiple values (eg, texture sample), rather
                 * than the split nodes that point back to that instruction.
                 * This isn't quite right, because it may be part of a larger
                 * group, such as:
                 *
                 *     sam (f32)(xyzw)r0.x, ...
                 *     add r1.x, ...
                 *     add r1.y, ...
                 *     sam (f32)(xyzw)r2.x, r0.w  <-- (r0.w, r1.x, r1.y)
                 *
                 * need to come up with a better way to handle that case.
                 */
                if (instr->address) {
                        *sz = instr->regs[0]->size;
                } else {
                        *sz = util_last_bit(instr->regs[0]->wrmask);
                }
                *off = 0;
                d = instr;
        }

        if (d->opc == OPC_META_SPLIT) {
                struct ir3_instruction *dd;
                int dsz, doff;

                dd = get_definer(ctx, d->regs[1]->instr, &dsz, &doff);

                /* by definition, should come before: */
                ra_assert(ctx, instr_before(dd, d));

                *sz = MAX2(*sz, dsz);

                if (instr->opc == OPC_META_SPLIT)
                        *off = MAX2(*off, instr->split.off);

                d = dd;
        }

        ra_assert(ctx, d->opc != OPC_META_SPLIT);

        id->defn = d;
        id->sz = *sz;
        id->off = *off;

        return d;
}

static void
ra_block_find_definers(struct ir3_ra_ctx *ctx, struct ir3_block *block)
{
        foreach_instr (instr, &block->instr_list) {
                struct ir3_ra_instr_data *id = &ctx->instrd[instr->ip];
                if (instr->regs_count == 0)
                        continue;
                /* couple special cases: */
                if (writes_addr0(instr) || writes_addr1(instr) || writes_pred(instr)) {
                        id->cls = -1;
                } else if (instr->regs[0]->flags & IR3_REG_ARRAY) {
                        id->cls = total_class_count;
                } else {
                        /* and the normal case: */
                        id->defn = get_definer(ctx, instr, &id->sz, &id->off);
                        id->cls = ra_size_to_class(id->sz, is_half(id->defn), is_high(id->defn));

                        /* this is a bit of duct-tape.. if we have a scenario like:
                         *
                         *   sam (f32)(x) out.x, ...
                         *   sam (f32)(x) out.y, ...
                         *
                         * Then the fanout/split meta instructions for the two different
                         * tex instructions end up grouped as left/right neighbors.  The
                         * upshot is that in when you get_definer() on one of the meta:fo's
                         * you get definer as the first sam with sz=2, but when you call
                         * get_definer() on the either of the sam's you get itself as the
                         * definer with sz=1.
                         *
                         * (We actually avoid this scenario exactly, the neighbor links
                         * prevent one of the output mov's from being eliminated, so this
                         * hack should be enough.  But probably we need to rethink how we
                         * find the "defining" instruction.)
                         *
                         * TODO how do we figure out offset properly...
                         */
                        if (id->defn != instr) {
                                struct ir3_ra_instr_data *did = &ctx->instrd[id->defn->ip];
                                if (did->sz < id->sz) {
                                        did->sz = id->sz;
                                        did->cls = id->cls;
                                }
                        }
                }
        }
}

/* give each instruction a name (and ip), and count up the # of names
 * of each class
 */
static void
ra_block_name_instructions(struct ir3_ra_ctx *ctx, struct ir3_block *block)
{
        foreach_instr (instr, &block->instr_list) {
                struct ir3_ra_instr_data *id = &ctx->instrd[instr->ip];

#ifdef DEBUG
                instr->name = ~0;
#endif

                ctx->instr_cnt++;

                if (!writes_gpr(instr))
                        continue;

                if (id->defn != instr)
                        continue;

                /* In scalar pass, collect/split don't get their own names,
                 * but instead inherit them from their src(s):
                 *
                 * Possibly we don't need this because of scalar_name(), but
                 * it does make the ir3_print() dumps easier to read.
                 */
                if (ctx->scalar_pass) {
                        if (instr->opc == OPC_META_SPLIT) {
                                instr->name = instr->regs[1]->instr->name + instr->split.off;
                                continue;
                        }

                        if (instr->opc == OPC_META_COLLECT) {
                                instr->name = instr->regs[1]->instr->name;
                                continue;
                        }
                }

                /* arrays which don't fit in one of the pre-defined class
                 * sizes are pre-colored:
                 */
                if ((id->cls >= 0) && (id->cls < total_class_count)) {
                        /* in the scalar pass, we generate a name for each
                         * scalar component, instr->name is the name of the
                         * first component.
                         */
                        unsigned n = ctx->scalar_pass ? dest_regs(instr) : 1;
                        instr->name = ctx->class_alloc_count[id->cls];
                        ctx->class_alloc_count[id->cls] += n;
                        ctx->alloc_count += n;
                }
        }
}

/**
 * Set a value for max register target.
 *
 * Currently this just rounds up to a multiple of full-vec4 (ie. the
 * granularity that we configure the hw for.. there is no point to
 * using r3.x if you aren't going to make r3.yzw available).  But
 * in reality there seems to be multiple thresholds that affect the
 * number of waves.. and we should round up the target to the next
 * threshold when we round-robin registers, to give postsched more
 * options.  When we understand that better, this is where we'd
 * implement that.
 */
static void
ra_set_register_target(struct ir3_ra_ctx *ctx, unsigned max_target)
{
        const unsigned hvec4 = 4;
        const unsigned vec4 = 2 * hvec4;

        ctx->max_target = align(max_target, vec4);

        d("New max_target=%u", ctx->max_target);
}

static int
pick_in_range(BITSET_WORD *regs, unsigned min, unsigned max)
{
        for (unsigned i = min; i <= max; i++) {
                if (BITSET_TEST(regs, i)) {
                        return i;
                }
        }
        return -1;
}

static int
pick_in_range_rev(BITSET_WORD *regs, int min, int max)
{
        for (int i = max; i >= min; i--) {
                if (BITSET_TEST(regs, i)) {
                        return i;
                }
        }
        return -1;
}

/* register selector for the a6xx+ merged register file: */
static unsigned int
ra_select_reg_merged(unsigned int n, BITSET_WORD *regs, void *data)
{
        struct ir3_ra_ctx *ctx = data;
        unsigned int class = ra_get_node_class(ctx->g, n);
        bool half, high;
        int sz = ra_class_to_size(class, &half, &high);

        assert (sz > 0);

        /* dimensions within the register class: */
        unsigned max_target, start;

        /* the regs bitset will include *all* of the virtual regs, but we lay
         * out the different classes consecutively in the virtual register
         * space.  So we just need to think about the base offset of a given
         * class within the virtual register space, and offset the register
         * space we search within by that base offset.
         */
        unsigned base;

        /* TODO I think eventually we want to round-robin in vector pass
         * as well, but needs some more work to calculate # of live vals
         * for this.  (Maybe with some work, we could just figure out
         * the scalar target and use that, since that is what we care
         * about in the end.. but that would mean setting up use-def/
         * liveranges for scalar pass before doing vector pass.)
         *
         * For now, in the vector class, just move assignments for scalar
         * vals higher to hopefully prevent them from limiting where vecN
         * values can be placed.  Since the scalar values are re-assigned
         * in the 2nd pass, we don't really care where they end up in the
         * vector pass.
         */
        if (!ctx->scalar_pass) {
                base = ctx->set->gpr_to_ra_reg[class][0];
                if (high) {
                        max_target = HIGH_CLASS_REGS(class - HIGH_OFFSET);
                } else if (half) {
                        max_target = HALF_CLASS_REGS(class - HALF_OFFSET);
                } else {
                        max_target = CLASS_REGS(class);
                }

                if ((sz == 1) && !high) {
                        return pick_in_range_rev(regs, base, base + max_target);
                } else {
                        return pick_in_range(regs, base, base + max_target);
                }
        } else {
                ra_assert(ctx, sz == 1);
        }

        /* NOTE: this is only used in scalar pass, so the register
         * class will be one of the scalar classes (ie. idx==0):
         */
        base = ctx->set->gpr_to_ra_reg[class][0];
        if (high) {
                max_target = HIGH_CLASS_REGS(0);
                start = 0;
        } else if (half) {
                max_target = ctx->max_target;
                start = ctx->start_search_reg;
        } else {
                max_target = ctx->max_target / 2;
                start = ctx->start_search_reg;
        }

        /* For cat4 instructions, if the src reg is already assigned, and
         * avail to pick, use it.  Because this doesn't introduce unnecessary
         * dependencies, and it potentially avoids needing (ss) syncs to
         * for write after read hazards:
         */
        struct ir3_instruction *instr = name_to_instr(ctx, n);
        if (is_sfu(instr)) {
                struct ir3_register *src = instr->regs[1];
                int src_n;

                if ((src->flags & IR3_REG_ARRAY) && !(src->flags & IR3_REG_RELATIV)) {
                        struct ir3_array *arr = ir3_lookup_array(ctx->ir, src->array.id);
                        src_n = arr->base + src->array.offset;
                } else {
                        src_n = scalar_name(ctx, src->instr, 0);
                }

                unsigned reg = ra_get_node_reg(ctx->g, src_n);

                /* Check if the src register has been assigned yet: */
                if (reg != NO_REG) {
                        if (BITSET_TEST(regs, reg)) {
                                return reg;
                        }
                }
        }

        int r = pick_in_range(regs, base + start, base + max_target);
        if (r < 0) {
                /* wrap-around: */
                r = pick_in_range(regs, base, base + start);
        }

        if (r < 0) {
                /* overflow, we need to increase max_target: */
                ra_set_register_target(ctx, ctx->max_target + 1);
                return ra_select_reg_merged(n, regs, data);
        }

        if (class == ctx->set->half_classes[0]) {
                int n = r - base;
                ctx->start_search_reg = (n + 1) % ctx->max_target;
        } else if (class == ctx->set->classes[0]) {
                int n = (r - base) * 2;
                ctx->start_search_reg = (n + 1) % ctx->max_target;
        }

        return r;
}

static void
ra_init(struct ir3_ra_ctx *ctx)
{
        unsigned n, base;

        ir3_clear_mark(ctx->ir);
        n = ir3_count_instructions_ra(ctx->ir);

        ctx->instrd = rzalloc_array(NULL, struct ir3_ra_instr_data, n);

        foreach_block (block, &ctx->ir->block_list) {
                ra_block_find_definers(ctx, block);
        }

        foreach_block (block, &ctx->ir->block_list) {
                ra_block_name_instructions(ctx, block);
        }

        /* figure out the base register name for each class.  The
         * actual ra name is class_base[cls] + instr->name;
         */
        ctx->class_base[0] = 0;
        for (unsigned i = 1; i <= total_class_count; i++) {
                ctx->class_base[i] = ctx->class_base[i-1] +
                                ctx->class_alloc_count[i-1];
        }

        /* and vreg names for array elements: */
        base = ctx->class_base[total_class_count];
        foreach_array (arr, &ctx->ir->array_list) {
                arr->base = base;
                ctx->class_alloc_count[total_class_count] += arr->length;
                base += arr->length;
        }
        ctx->alloc_count += ctx->class_alloc_count[total_class_count];

        /* Add vreg names for r0.xyz */
        ctx->r0_xyz_nodes = ctx->alloc_count;
        ctx->alloc_count += 3;
        ctx->hr0_xyz_nodes = ctx->alloc_count;
        ctx->alloc_count += 3;

        /* Add vreg name for prefetch-exclusion range: */
        ctx->prefetch_exclude_node = ctx->alloc_count++;

        if (RA_DEBUG) {
                d("INSTRUCTION VREG NAMES:");
                foreach_block (block, &ctx->ir->block_list) {
                        foreach_instr (instr, &block->instr_list) {
                                if (!ctx->instrd[instr->ip].defn)
                                        continue;
                                if (!writes_gpr(instr))
                                        continue;
                                di(instr, "%04u", scalar_name(ctx, instr, 0));
                        }
                }
                d("ARRAY VREG NAMES:");
                foreach_array (arr, &ctx->ir->array_list) {
                        d("%04u: arr%u", arr->base, arr->id);
                }
                d("EXTRA VREG NAMES:");
                d("%04u: r0_xyz_nodes", ctx->r0_xyz_nodes);
                d("%04u: hr0_xyz_nodes", ctx->hr0_xyz_nodes);
                d("%04u: prefetch_exclude_node", ctx->prefetch_exclude_node);
        }

        ctx->g = ra_alloc_interference_graph(ctx->set->regs, ctx->alloc_count);
        ralloc_steal(ctx->g, ctx->instrd);
        ctx->def = rzalloc_array(ctx->g, unsigned, ctx->alloc_count);
        ctx->use = rzalloc_array(ctx->g, unsigned, ctx->alloc_count);

        /* TODO add selector callback for split (pre-a6xx) register file: */
        if (ctx->v->mergedregs) {
                ra_set_select_reg_callback(ctx->g, ra_select_reg_merged, ctx);

                if (ctx->scalar_pass) {
                        ctx->name_to_instr = _mesa_hash_table_create(ctx->g,
                                        _mesa_hash_int, _mesa_key_int_equal);
                }
        }
}

/* Map the name back to instruction: */
static struct ir3_instruction *
name_to_instr(struct ir3_ra_ctx *ctx, unsigned name)
{
        ra_assert(ctx, !name_is_array(ctx, name));
        struct hash_entry *entry = _mesa_hash_table_search(ctx->name_to_instr, &name);
        if (entry)
                return entry->data;
        ra_unreachable(ctx, "invalid instr name");
        return NULL;
}

static bool
name_is_array(struct ir3_ra_ctx *ctx, unsigned name)
{
        return name >= ctx->class_base[total_class_count];
}

static struct ir3_array *
name_to_array(struct ir3_ra_ctx *ctx, unsigned name)
{
        ra_assert(ctx, name_is_array(ctx, name));
        foreach_array (arr, &ctx->ir->array_list) {
                if (name < (arr->base + arr->length))
                        return arr;
        }
        ra_unreachable(ctx, "invalid array name");
        return NULL;
}

static void
ra_destroy(struct ir3_ra_ctx *ctx)
{
        ralloc_free(ctx->g);
}

static void
__def(struct ir3_ra_ctx *ctx, struct ir3_ra_block_data *bd, unsigned name,
                struct ir3_instruction *instr)
{
        ra_assert(ctx, name < ctx->alloc_count);

        /* split/collect do not actually define any real value */
        if ((instr->opc == OPC_META_SPLIT) || (instr->opc == OPC_META_COLLECT))
                return;

        /* defined on first write: */
        if (!ctx->def[name])
                ctx->def[name] = instr->ip;
        ctx->use[name] = MAX2(ctx->use[name], instr->ip);
        BITSET_SET(bd->def, name);
}

static void
__use(struct ir3_ra_ctx *ctx, struct ir3_ra_block_data *bd, unsigned name,
                struct ir3_instruction *instr)
{
        ra_assert(ctx, name < ctx->alloc_count);
        ctx->use[name] = MAX2(ctx->use[name], instr->ip);
        if (!BITSET_TEST(bd->def, name))
                BITSET_SET(bd->use, name);
}

static void
ra_block_compute_live_ranges(struct ir3_ra_ctx *ctx, struct ir3_block *block)
{
        struct ir3_ra_block_data *bd;
        unsigned bitset_words = BITSET_WORDS(ctx->alloc_count);

#define def(name, instr) __def(ctx, bd, name, instr)
#define use(name, instr) __use(ctx, bd, name, instr)

        bd = rzalloc(ctx->g, struct ir3_ra_block_data);

        bd->def     = rzalloc_array(bd, BITSET_WORD, bitset_words);
        bd->use     = rzalloc_array(bd, BITSET_WORD, bitset_words);
        bd->livein  = rzalloc_array(bd, BITSET_WORD, bitset_words);
        bd->liveout = rzalloc_array(bd, BITSET_WORD, bitset_words);

        block->data = bd;

        struct ir3_instruction *first_non_input = NULL;
        foreach_instr (instr, &block->instr_list) {
                if (instr->opc != OPC_META_INPUT) {
                        first_non_input = instr;
                        break;
                }
        }

        foreach_instr (instr, &block->instr_list) {
                foreach_def (name, ctx, instr) {
                        if (name_is_array(ctx, name)) {
                                struct ir3_array *arr = name_to_array(ctx, name);

                                arr->start_ip = MIN2(arr->start_ip, instr->ip);
                                arr->end_ip = MAX2(arr->end_ip, instr->ip);

                                for (unsigned i = 0; i < arr->length; i++) {
                                        unsigned name = arr->base + i;
                                        if(arr->half)
                                                ra_set_node_class(ctx->g, name, ctx->set->half_classes[0]);
                                        else
                                                ra_set_node_class(ctx->g, name, ctx->set->classes[0]);
                                }
                        } else {
                                struct ir3_ra_instr_data *id = &ctx->instrd[instr->ip];
                                if (is_high(instr)) {
                                        ra_set_node_class(ctx->g, name,
                                                        ctx->set->high_classes[id->cls - HIGH_OFFSET]);
                                } else if (is_half(instr)) {
                                        ra_set_node_class(ctx->g, name,
                                                        ctx->set->half_classes[id->cls - HALF_OFFSET]);
                                } else {
                                        ra_set_node_class(ctx->g, name,
                                                        ctx->set->classes[id->cls]);
                                }
                        }

                        def(name, instr);

                        if ((instr->opc == OPC_META_INPUT) && first_non_input)
                                use(name, first_non_input);

                        /* Texture instructions with writemasks can be treated as smaller
                         * vectors (or just scalars!) to allocate knowing that the
                         * masked-out regs won't be written, but we need to make sure that
                         * the start of the vector doesn't come before the first register
                         * or we'll wrap.
                         */
                        if (is_tex_or_prefetch(instr)) {
                                int writemask_skipped_regs = ffs(instr->regs[0]->wrmask) - 1;
                                int r0_xyz = is_half(instr) ?
                                        ctx->hr0_xyz_nodes : ctx->r0_xyz_nodes;
                                for (int i = 0; i < writemask_skipped_regs; i++)
                                        ra_add_node_interference(ctx->g, name, r0_xyz + i);
                        }

                        /* Pre-fetched textures have a lower limit for bits to encode dst
                         * register, so add additional interference with registers above
                         * that limit.
                         */
                        if (instr->opc == OPC_META_TEX_PREFETCH) {
                                ra_add_node_interference(ctx->g, name,
                                                ctx->prefetch_exclude_node);
                        }
                }

                foreach_use (name, ctx, instr) {
                        if (name_is_array(ctx, name)) {
                                struct ir3_array *arr = name_to_array(ctx, name);

                                arr->start_ip = MIN2(arr->start_ip, instr->ip);
                                arr->end_ip = MAX2(arr->end_ip, instr->ip);

                                /* NOTE: arrays are not SSA so unconditionally
                                 * set use bit:
                                 */
                                BITSET_SET(bd->use, name);
                        }

                        use(name, instr);
                }

                foreach_name (name, ctx, instr) {
                        /* split/collect instructions have duplicate names
                         * as real instructions, so they skip the hashtable:
                         */
                        if (ctx->name_to_instr && !((instr->opc == OPC_META_SPLIT) ||
                                        (instr->opc == OPC_META_COLLECT))) {
                                /* this is slightly annoying, we can't just use an
                                 * integer on the stack
                                 */
                                unsigned *key = ralloc(ctx->name_to_instr, unsigned);
                                *key = name;
                                ra_assert(ctx, !_mesa_hash_table_search(ctx->name_to_instr, key));
                                _mesa_hash_table_insert(ctx->name_to_instr, key, instr);
                        }
                }
        }
}

static bool
ra_compute_livein_liveout(struct ir3_ra_ctx *ctx)
{
        unsigned bitset_words = BITSET_WORDS(ctx->alloc_count);
        bool progress = false;

        foreach_block (block, &ctx->ir->block_list) {
                struct ir3_ra_block_data *bd = block->data;

                /* update livein: */
                for (unsigned i = 0; i < bitset_words; i++) {
                        /* anything used but not def'd within a block is
                         * by definition a live value coming into the block:
                         */
                        BITSET_WORD new_livein =
                                (bd->use[i] | (bd->liveout[i] & ~bd->def[i]));

                        if (new_livein & ~bd->livein[i]) {
                                bd->livein[i] |= new_livein;
                                progress = true;
                        }
                }

                /* update liveout: */
                for (unsigned j = 0; j < ARRAY_SIZE(block->successors); j++) {
                        struct ir3_block *succ = block->successors[j];
                        struct ir3_ra_block_data *succ_bd;

                        if (!succ)
                                continue;

                        succ_bd = succ->data;

                        for (unsigned i = 0; i < bitset_words; i++) {
                                /* add anything that is livein in a successor block
                                 * to our liveout:
                                 */
                                BITSET_WORD new_liveout =
                                        (succ_bd->livein[i] & ~bd->liveout[i]);

                                if (new_liveout) {
                                        bd->liveout[i] |= new_liveout;
                                        progress = true;
                                }
                        }
                }
        }

        return progress;
}

static void
print_bitset(const char *name, BITSET_WORD *bs, unsigned cnt)
{
        bool first = true;
        debug_printf("RA:  %s:", name);
        for (unsigned i = 0; i < cnt; i++) {
                if (BITSET_TEST(bs, i)) {
                        if (!first)
                                debug_printf(",");
                        debug_printf(" %04u", i);
                        first = false;
                }
        }
        debug_printf("\n");
}

/* size of one component of instruction result, ie. half vs full: */
static unsigned
live_size(struct ir3_instruction *instr)
{
        if (is_half(instr)) {
                return 1;
        } else if (is_high(instr)) {
                /* doesn't count towards footprint */
                return 0;
        } else {
                return 2;
        }
}

static unsigned
name_size(struct ir3_ra_ctx *ctx, unsigned name)
{
        if (name_is_array(ctx, name)) {
                struct ir3_array *arr = name_to_array(ctx, name);
                return arr->half ? 1 : 2;
        } else {
                struct ir3_instruction *instr = name_to_instr(ctx, name);
                /* in scalar pass, each name represents on scalar value,
                 * half or full precision
                 */
                return live_size(instr);
        }
}

static unsigned
ra_calc_block_live_values(struct ir3_ra_ctx *ctx, struct ir3_block *block)
{
        struct ir3_ra_block_data *bd = block->data;
        unsigned name;

        ra_assert(ctx, ctx->name_to_instr);

        /* TODO this gets a bit more complicated in non-scalar pass.. but
         * possibly a lowball estimate is fine to start with if we do
         * round-robin in non-scalar pass?  Maybe we just want to handle
         * that in a different fxn?
         */
        ra_assert(ctx, ctx->scalar_pass);

        BITSET_WORD *live =
                rzalloc_array(bd, BITSET_WORD, BITSET_WORDS(ctx->alloc_count));

        /* Add the live input values: */
        unsigned livein = 0;
        BITSET_FOREACH_SET (name, bd->livein, ctx->alloc_count) {
                livein += name_size(ctx, name);
                BITSET_SET(live, name);
        }

        d("---------------------");
        d("block%u: LIVEIN: %u", block_id(block), livein);

        unsigned max = livein;
        int cur_live = max;

        /* Now that we know the live inputs to the block, iterate the
         * instructions adjusting the current # of live values as we
         * see their last use:
         */
        foreach_instr (instr, &block->instr_list) {
                if (RA_DEBUG)
                        print_bitset("LIVE", live, ctx->alloc_count);
                di(instr, "CALC");

                unsigned new_live = 0;    /* newly live values */
                unsigned new_dead = 0;    /* newly no-longer live values */
                unsigned next_dead = 0;   /* newly dead following this instr */

                foreach_def (name, ctx, instr) {
                        /* NOTE: checking ctx->def filters out things like split/
                         * collect which are just redefining existing live names
                         * or array writes to already live array elements:
                         */
                        if (ctx->def[name] != instr->ip)
                                continue;
                        new_live += live_size(instr);
                        d("NEW_LIVE: %u (new_live=%u, use=%u)", name, new_live, ctx->use[name]);
                        BITSET_SET(live, name);
                        /* There can be cases where this is *also* the last use
                         * of a value, for example instructions that write multiple
                         * values, only some of which are used.  These values are
                         * dead *after* (rather than during) this instruction.
                         */
                        if (ctx->use[name] != instr->ip)
                                continue;
                        next_dead += live_size(instr);
                        d("NEXT_DEAD: %u (next_dead=%u)", name, next_dead);
                        BITSET_CLEAR(live, name);
                }

                /* To be more resilient against special cases where liverange
                 * is extended (like first_non_input), rather than using the
                 * foreach_use() iterator, we iterate the current live values
                 * instead:
                 */
                BITSET_FOREACH_SET (name, live, ctx->alloc_count) {
                        /* Is this the last use? */
                        if (ctx->use[name] != instr->ip)
                                continue;
                        new_dead += name_size(ctx, name);
                        d("NEW_DEAD: %u (new_dead=%u)", name, new_dead);
                        BITSET_CLEAR(live, name);
                }

                cur_live += new_live;
                cur_live -= new_dead;

                ra_assert(ctx, cur_live >= 0);
                d("CUR_LIVE: %u", cur_live);

                max = MAX2(max, cur_live);

                /* account for written values which are not used later,
                 * but after updating max (since they are for one cycle
                 * live)
                 */
                cur_live -= next_dead;
                ra_assert(ctx, cur_live >= 0);

                if (RA_DEBUG) {
                        unsigned cnt = 0;
                        BITSET_FOREACH_SET (name, live, ctx->alloc_count) {
                                cnt += name_size(ctx, name);
                        }
                        ra_assert(ctx, cur_live == cnt);
                }
        }

        d("block%u max=%u", block_id(block), max);

        /* the remaining live should match liveout (for extra sanity testing): */
        if (RA_DEBUG) {
                unsigned new_dead = 0;
                BITSET_FOREACH_SET (name, live, ctx->alloc_count) {
                        /* Is this the last use? */
                        if (ctx->use[name] != block->end_ip)
                                continue;
                        new_dead += name_size(ctx, name);
                        d("NEW_DEAD: %u (new_dead=%u)", name, new_dead);
                        BITSET_CLEAR(live, name);
                }
                unsigned liveout = 0;
                BITSET_FOREACH_SET (name, bd->liveout, ctx->alloc_count) {
                        liveout += name_size(ctx, name);
                        BITSET_CLEAR(live, name);
                }

                if (cur_live != liveout) {
                        print_bitset("LEAKED", live, ctx->alloc_count);
                        /* TODO there are a few edge cases where live-range extension
                         * tells us a value is livein.  But not used by the block or
                         * liveout for the block.  Possibly a bug in the liverange
                         * extension.  But for now leave the assert disabled:
                        ra_assert(ctx, cur_live == liveout);
                         */
                }
        }

        ralloc_free(live);

        return max;
}

static unsigned
ra_calc_max_live_values(struct ir3_ra_ctx *ctx)
{
        unsigned max = 0;

        foreach_block (block, &ctx->ir->block_list) {
                unsigned block_live = ra_calc_block_live_values(ctx, block);
                max = MAX2(max, block_live);
        }

        return max;
}

static void
ra_add_interference(struct ir3_ra_ctx *ctx)
{
        struct ir3 *ir = ctx->ir;

        /* initialize array live ranges: */
        foreach_array (arr, &ir->array_list) {
                arr->start_ip = ~0;
                arr->end_ip = 0;
        }

        /* set up the r0.xyz precolor regs. */
        for (int i = 0; i < 3; i++) {
                ra_set_node_reg(ctx->g, ctx->r0_xyz_nodes + i, i);
                ra_set_node_reg(ctx->g, ctx->hr0_xyz_nodes + i,
                                ctx->set->first_half_reg + i);
        }

        /* pre-color node that conflict with half/full regs higher than what
         * can be encoded for tex-prefetch:
         */
        ra_set_node_reg(ctx->g, ctx->prefetch_exclude_node,
                        ctx->set->prefetch_exclude_reg);

        /* compute live ranges (use/def) on a block level, also updating
         * block's def/use bitmasks (used below to calculate per-block
         * livein/liveout):
         */
        foreach_block (block, &ir->block_list) {
                ra_block_compute_live_ranges(ctx, block);
        }

        /* update per-block livein/liveout: */
        while (ra_compute_livein_liveout(ctx)) {}

        if (RA_DEBUG) {
                d("AFTER LIVEIN/OUT:");
                foreach_block (block, &ir->block_list) {
                        struct ir3_ra_block_data *bd = block->data;
                        d("block%u:", block_id(block));
                        print_bitset("  def", bd->def, ctx->alloc_count);
                        print_bitset("  use", bd->use, ctx->alloc_count);
                        print_bitset("  l/i", bd->livein, ctx->alloc_count);
                        print_bitset("  l/o", bd->liveout, ctx->alloc_count);
                }
                foreach_array (arr, &ir->array_list) {
                        d("array%u:", arr->id);
                        d("   length:   %u", arr->length);
                        d("   start_ip: %u", arr->start_ip);
                        d("   end_ip:   %u", arr->end_ip);
                }
        }

        /* extend start/end ranges based on livein/liveout info from cfg: */
        foreach_block (block, &ir->block_list) {
                struct ir3_ra_block_data *bd = block->data;

                for (unsigned i = 0; i < ctx->alloc_count; i++) {
                        if (BITSET_TEST(bd->livein, i)) {
                                ctx->def[i] = MIN2(ctx->def[i], block->start_ip);
                                ctx->use[i] = MAX2(ctx->use[i], block->start_ip);
                        }

                        if (BITSET_TEST(bd->liveout, i)) {
                                ctx->def[i] = MIN2(ctx->def[i], block->end_ip);
                                ctx->use[i] = MAX2(ctx->use[i], block->end_ip);
                        }
                }

                foreach_array (arr, &ctx->ir->array_list) {
                        for (unsigned i = 0; i < arr->length; i++) {
                                if (BITSET_TEST(bd->livein, i + arr->base)) {
                                        arr->start_ip = MIN2(arr->start_ip, block->start_ip);
                                }
                                if (BITSET_TEST(bd->liveout, i + arr->base)) {
                                        arr->end_ip = MAX2(arr->end_ip, block->end_ip);
                                }
                        }
                }
        }

        if (ctx->name_to_instr) {
                unsigned max = ra_calc_max_live_values(ctx);
                ra_set_register_target(ctx, max);
        }

        for (unsigned i = 0; i < ctx->alloc_count; i++) {
                for (unsigned j = 0; j < ctx->alloc_count; j++) {
                        if (intersects(ctx->def[i], ctx->use[i],
                                        ctx->def[j], ctx->use[j])) {
                                ra_add_node_interference(ctx->g, i, j);
                        }
                }
        }
}

/* NOTE: instr could be NULL for IR3_REG_ARRAY case, for the first
 * array access(es) which do not have any previous access to depend
 * on from scheduling point of view
 */
static void
reg_assign(struct ir3_ra_ctx *ctx, struct ir3_register *reg,
                struct ir3_instruction *instr)
{
        struct ir3_ra_instr_data *id;

        if (reg->flags & IR3_REG_ARRAY) {
                struct ir3_array *arr =
                        ir3_lookup_array(ctx->ir, reg->array.id);
                unsigned name = arr->base + reg->array.offset;
                unsigned r = ra_get_node_reg(ctx->g, name);
                unsigned num = ctx->set->ra_reg_to_gpr[r];

                if (reg->flags & IR3_REG_RELATIV) {
                        reg->array.offset = num;
                } else {
                        reg->num = num;
                        reg->flags &= ~IR3_REG_SSA;
                }

                reg->flags &= ~IR3_REG_ARRAY;
        } else if ((id = &ctx->instrd[instr->ip]) && id->defn) {
                unsigned first_component = 0;

                /* Special case for tex instructions, which may use the wrmask
                 * to mask off the first component(s).  In the scalar pass,
                 * this means the masked off component(s) are not def'd/use'd,
                 * so we get a bogus value when we ask the register_allocate
                 * algo to get the assigned reg for the unused/untouched
                 * component.  So we need to consider the first used component:
                 */
                if (ctx->scalar_pass && is_tex_or_prefetch(id->defn)) {
                        unsigned n = ffs(id->defn->regs[0]->wrmask);
                        ra_assert(ctx, n > 0);
                        first_component = n - 1;
                }

                unsigned name = scalar_name(ctx, id->defn, first_component);
                unsigned r = ra_get_node_reg(ctx->g, name);
                unsigned num = ctx->set->ra_reg_to_gpr[r] + id->off;

                ra_assert(ctx, !(reg->flags & IR3_REG_RELATIV));

                ra_assert(ctx, num >= first_component);

                if (is_high(id->defn))
                        num += FIRST_HIGH_REG;

                reg->num = num - first_component;

                reg->flags &= ~IR3_REG_SSA;

                if (is_half(id->defn))
                        reg->flags |= IR3_REG_HALF;
        }
}

/* helper to determine which regs to assign in which pass: */
static bool
should_assign(struct ir3_ra_ctx *ctx, struct ir3_instruction *instr)
{
        if ((instr->opc == OPC_META_SPLIT) &&
                        (util_bitcount(instr->regs[1]->wrmask) > 1))
                return !ctx->scalar_pass;
        if ((instr->opc == OPC_META_COLLECT) &&
                        (util_bitcount(instr->regs[0]->wrmask) > 1))
                return !ctx->scalar_pass;
        return ctx->scalar_pass;
}

static void
ra_block_alloc(struct ir3_ra_ctx *ctx, struct ir3_block *block)
{
        foreach_instr (instr, &block->instr_list) {

                if (writes_gpr(instr)) {
                        if (should_assign(ctx, instr)) {
                                reg_assign(ctx, instr->regs[0], instr);
                        }
                }

                foreach_src_n (reg, n, instr) {
                        struct ir3_instruction *src = reg->instr;

                        if (src && !should_assign(ctx, src) && !should_assign(ctx, instr))
                                continue;

                        if (src && should_assign(ctx, instr))
                                reg_assign(ctx, src->regs[0], src);

                        /* Note: reg->instr could be null for IR3_REG_ARRAY */
                        if (src || (reg->flags & IR3_REG_ARRAY))
                                reg_assign(ctx, instr->regs[n+1], src);
                }
        }

        /* We need to pre-color outputs for the scalar pass in
         * ra_precolor_assigned(), so we need to actually assign
         * them in the first pass:
         */
        if (!ctx->scalar_pass) {
                foreach_input (in, ctx->ir) {
                        reg_assign(ctx, in->regs[0], in);
                }
                foreach_output (out, ctx->ir) {
                        reg_assign(ctx, out->regs[0], out);
                }
        }
}

static void
assign_arr_base(struct ir3_ra_ctx *ctx, struct ir3_array *arr,
                struct ir3_instruction **precolor, unsigned nprecolor)
{
        /* In the mergedregs case, we convert full precision arrays
         * to their effective half-precision base, and find conflicts
         * amongst all other arrays/inputs.
         *
         * In the splitregs case (halfreg file and fullreg file do
         * not conflict), we ignore arrays and other pre-colors that
         * are not the same precision.
         */
        bool mergedregs = ctx->v->mergedregs;
        unsigned base = 0;

        /* figure out what else we conflict with which has already
         * been assigned:
         */
retry:
        foreach_array (arr2, &ctx->ir->array_list) {
                if (arr2 == arr)
                        break;
                ra_assert(ctx, arr2->start_ip <= arr2->end_ip);

                unsigned base2 = arr2->reg;
                unsigned len2  = arr2->length;
                unsigned len   = arr->length;

                if (mergedregs) {
                        /* convert into half-reg space: */
                        if (!arr2->half) {
                                base2 *= 2;
                                len2  *= 2;
                        }
                        if (!arr->half) {
                                len   *= 2;
                        }
                } else if (arr2->half != arr->half) {
                        /* for split-register-file mode, we only conflict with
                         * other arrays of same precision:
                         */
                        continue;
                }

                /* if it intersects with liverange AND register range.. */
                if (intersects(arr->start_ip, arr->end_ip,
                                arr2->start_ip, arr2->end_ip) &&
                        intersects(base, base + len,
                                base2, base2 + len2)) {
                        base = MAX2(base, base2 + len2);
                        goto retry;
                }
        }

        /* also need to not conflict with any pre-assigned inputs: */
        for (unsigned i = 0; i < nprecolor; i++) {
                struct ir3_instruction *instr = precolor[i];

                if (!instr || (instr->flags & IR3_INSTR_UNUSED))
                        continue;

                struct ir3_ra_instr_data *id = &ctx->instrd[instr->ip];

                /* only consider the first component: */
                if (id->off > 0)
                        continue;

                unsigned name   = ra_name(ctx, id);
                unsigned regid  = instr->regs[0]->num;
                unsigned reglen = class_sizes[id->cls];
                unsigned len    = arr->length;

                if (mergedregs) {
                        /* convert into half-reg space: */
                        if (!is_half(instr)) {
                                regid  *= 2;
                                reglen *= 2;
                        }
                        if (!arr->half) {
                                len   *= 2;
                        }
                } else if (is_half(instr) != arr->half) {
                        /* for split-register-file mode, we only conflict with
                         * other arrays of same precision:
                         */
                        continue;
                }

                /* Check if array intersects with liverange AND register
                 * range of the input:
                 */
                if (intersects(arr->start_ip, arr->end_ip,
                                                ctx->def[name], ctx->use[name]) &&
                                intersects(base, base + len,
                                                regid, regid + reglen)) {
                        base = MAX2(base, regid + reglen);
                        goto retry;
                }
        }

        /* convert back from half-reg space to fullreg space: */
        if (mergedregs && !arr->half) {
                base = DIV_ROUND_UP(base, 2);
        }

        arr->reg = base;
}

/* handle pre-colored registers.  This includes "arrays" (which could be of
 * length 1, used for phi webs lowered to registers in nir), as well as
 * special shader input values that need to be pinned to certain registers.
 */
static void
ra_precolor(struct ir3_ra_ctx *ctx, struct ir3_instruction **precolor, unsigned nprecolor)
{
        for (unsigned i = 0; i < nprecolor; i++) {
                if (precolor[i] && !(precolor[i]->flags & IR3_INSTR_UNUSED)) {
                        struct ir3_instruction *instr = precolor[i];

                        if (instr->regs[0]->num == INVALID_REG)
                                continue;

                        struct ir3_ra_instr_data *id = &ctx->instrd[instr->ip];

                        ra_assert(ctx, !(instr->regs[0]->flags & (IR3_REG_HALF | IR3_REG_HIGH)));

                        /* 'base' is in scalar (class 0) but we need to map that
                         * the conflicting register of the appropriate class (ie.
                         * input could be vec2/vec3/etc)
                         *
                         * Note that the higher class (larger than scalar) regs
                         * are setup to conflict with others in the same class,
                         * so for example, R1 (scalar) is also the first component
                         * of D1 (vec2/double):
                         *
                         *    Single (base) |  Double
                         *    --------------+---------------
                         *       R0         |  D0
                         *       R1         |  D0 D1
                         *       R2         |     D1 D2
                         *       R3         |        D2
                         *           .. and so on..
                         */
                        unsigned regid = instr->regs[0]->num;
                        ra_assert(ctx, regid >= id->off);
                        regid -= id->off;

                        unsigned reg = ctx->set->gpr_to_ra_reg[id->cls][regid];
                        unsigned name = ra_name(ctx, id);
                        ra_set_node_reg(ctx->g, name, reg);
                }
        }

        /*
         * Pre-assign array elements:
         */
        foreach_array (arr, &ctx->ir->array_list) {

                if (arr->end_ip == 0)
                        continue;

                if (!ctx->scalar_pass)
                        assign_arr_base(ctx, arr, precolor, nprecolor);

                for (unsigned i = 0; i < arr->length; i++) {
                        unsigned cls = arr->half ? HALF_OFFSET : 0;

                        ra_set_node_reg(ctx->g,
                                        arr->base + i,   /* vreg name */
                                        ctx->set->gpr_to_ra_reg[cls][arr->reg + i]);
                }
        }

        if (ir3_shader_debug & IR3_DBG_OPTMSGS) {
                foreach_array (arr, &ctx->ir->array_list) {
                        unsigned first = arr->reg;
                        unsigned last  = arr->reg + arr->length - 1;
                        debug_printf("arr[%d] at r%d.%c->r%d.%c\n", arr->id,
                                        (first >> 2), "xyzw"[first & 0x3],
                                        (last >> 2), "xyzw"[last & 0x3]);
                }
        }
}

static void
precolor(struct ir3_ra_ctx *ctx, struct ir3_instruction *instr)
{
        struct ir3_ra_instr_data *id = &ctx->instrd[instr->ip];
        unsigned n = dest_regs(instr);
        for (unsigned i = 0; i < n; i++) {
                /* tex instructions actually have a wrmask, and
                 * don't touch masked out components.  So we
                 * shouldn't precolor them::
                 */
                if (is_tex_or_prefetch(instr) &&
                                !(instr->regs[0]->wrmask & (1 << i)))
                        continue;

                unsigned name = scalar_name(ctx, instr, i);
                unsigned regid = instr->regs[0]->num + i;

                if (instr->regs[0]->flags & IR3_REG_HIGH)
                        regid -= FIRST_HIGH_REG;

                unsigned vreg = ctx->set->gpr_to_ra_reg[id->cls][regid];
                ra_set_node_reg(ctx->g, name, vreg);
        }
}

/* pre-color non-scalar registers based on the registers assigned in previous
 * pass.  Do this by looking actually at the fanout instructions.
 */
static void
ra_precolor_assigned(struct ir3_ra_ctx *ctx)
{
        ra_assert(ctx, ctx->scalar_pass);

        foreach_block (block, &ctx->ir->block_list) {
                foreach_instr (instr, &block->instr_list) {

                        if (!writes_gpr(instr))
                                continue;

                        if (should_assign(ctx, instr))
                                continue;

                        precolor(ctx, instr);

                        foreach_src (src, instr) {
                                if (!src->instr)
                                        continue;
                                precolor(ctx, src->instr);
                        }
                }
        }
}

static int
ra_alloc(struct ir3_ra_ctx *ctx)
{
        if (!ra_allocate(ctx->g))
                return -1;

        foreach_block (block, &ctx->ir->block_list) {
                ra_block_alloc(ctx, block);
        }

        return 0;
}

/* if we end up with split/collect instructions with non-matching src
 * and dest regs, that means something has gone wrong.  Which makes it
 * a pretty good sanity check.
 */
static void
ra_sanity_check(struct ir3 *ir)
{
        foreach_block (block, &ir->block_list) {
                foreach_instr (instr, &block->instr_list) {
                        if (instr->opc == OPC_META_SPLIT) {
                                struct ir3_register *dst = instr->regs[0];
                                struct ir3_register *src = instr->regs[1];
                                debug_assert(dst->num == (src->num + instr->split.off));
                        } else if (instr->opc == OPC_META_COLLECT) {
                                struct ir3_register *dst = instr->regs[0];

                                foreach_src_n (src, n, instr) {
                                        debug_assert(dst->num == (src->num - n));
                                }
                        }
                }
        }
}

static int
ir3_ra_pass(struct ir3_shader_variant *v, struct ir3_instruction **precolor,
                unsigned nprecolor, bool scalar_pass)
{
        struct ir3_ra_ctx ctx = {
                        .v = v,
                        .ir = v->ir,
                        .set = v->mergedregs ?
                                v->ir->compiler->mergedregs_set : v->ir->compiler->set,
                        .scalar_pass = scalar_pass,
        };
        int ret;

        ret = setjmp(ctx.jmp_env);
        if (ret)
                goto fail;

        ra_init(&ctx);
        ra_add_interference(&ctx);
        ra_precolor(&ctx, precolor, nprecolor);
        if (scalar_pass)
                ra_precolor_assigned(&ctx);
        ret = ra_alloc(&ctx);

fail:
        ra_destroy(&ctx);

        return ret;
}

int
ir3_ra(struct ir3_shader_variant *v, struct ir3_instruction **precolor,
                unsigned nprecolor)
{
        int ret;

        /* First pass, assign the vecN (non-scalar) registers: */
        ret = ir3_ra_pass(v, precolor, nprecolor, false);
        if (ret)
                return ret;

        ir3_debug_print(v->ir, "AFTER: ir3_ra (1st pass)");

        /* Second pass, assign the scalar registers: */
        ret = ir3_ra_pass(v, precolor, nprecolor, true);
        if (ret)
                return ret;

        ir3_debug_print(v->ir, "AFTER: ir3_ra (2st pass)");

#ifdef DEBUG
#  define SANITY_CHECK DEBUG
#else
#  define SANITY_CHECK 0
#endif
        if (SANITY_CHECK)
                ra_sanity_check(v->ir);

        return ret;
}