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i915/corm: add temporary register tracking and dead temp release

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Track the last use of each SSA def and release temporary registers
as soon as they're dead, allowing more aggressive temp reuse.

Includes the register aliasing fix for mov/fneg: these ops alias
the def to the source register, so the source's lifetime must be
extended to match the def's to prevent premature release.

shader-db (I915_FS=nir): 52/403 compiled, 231 alu
shader-db (I915_FS=both): nir won 52 (26 identical, 16 tied, 9 better, 1 only),
  233 TGSI, 118 neither

Assisted-by: Claude
This commit is contained in:
Adam Jackson 2026-05-06 12:55:06 -04:00
parent c6be264c2d
commit 9a88dff9f4
1 changed files with 54 additions and 0 deletions
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54
src/gallium/drivers/i915/i915_fpc_nir.c
View file

@ -22,8 +22,51 @@ struct nir_to_i915 {
uint32_t *ureg_map;
unsigned ureg_map_size;
int *last_use;
int ip;
};
static bool
mark_last_use_cb(nir_src *src, void *state)
{
struct nir_to_i915 *c = state;
if (src->ssa->index < c->ureg_map_size)
c->last_use[src->ssa->index] = c->ip;
return true;
}
static void
compute_last_use(struct nir_to_i915 *c, nir_function_impl *impl)
{
c->ip = 0;
nir_foreach_block(block, impl) {
nir_foreach_instr(instr, block) {
nir_foreach_src(instr, mark_last_use_cb, c);
c->ip++;
}
}
}
static bool
release_if_last_use_cb(nir_src *src, void *state)
{
struct nir_to_i915 *c = state;
unsigned idx = src->ssa->index;
if (idx < c->ureg_map_size && c->last_use[idx] == c->ip) {
uint32_t ureg = c->ureg_map[idx];
if (GET_UREG_TYPE(ureg) == REG_TYPE_R)
i915_release_temp(c->p, GET_UREG_NR(ureg));
}
return true;
}
static void
release_dead_temps(struct nir_to_i915 *c, nir_instr *instr)
{
nir_foreach_src(instr, release_if_last_use_cb, c);
}
static void
set_ureg(struct nir_to_i915 *c, nir_def *def, uint32_t ureg)
{
@ -185,6 +228,9 @@ emit_alu(struct nir_to_i915 *c, nir_alu_instr *alu)
i915_release_temp(p, GET_UREG_NR(dest));
set_ureg(c, def, alu->op == nir_op_fneg ? negate(src0, 1, 1, 1, 1)
: src0);
unsigned src_idx = alu->src[0].src.ssa->index;
if (c->last_use[src_idx] == c->ip)
c->last_use[src_idx] = c->last_use[def->index];
return;
}
case nir_op_fabs:
@ -727,13 +773,20 @@ i915_translate_fragment_program_nir(struct i915_context *i915,
.opts = *opts,
.ureg_map_size = impl->ssa_alloc,
.ureg_map = CALLOC(impl->ssa_alloc, sizeof(uint32_t)),
.last_use = CALLOC(impl->ssa_alloc, sizeof(int)),
};
memset(c.last_use, -1, impl->ssa_alloc * sizeof(int));
compute_last_use(&c, impl);
c.ip = 0;
nir_foreach_block(block, impl) {
nir_foreach_instr(instr, block) {
emit_instr(&c, instr);
if (p->error[0])
break;
release_dead_temps(&c, instr);
c.ip++;
}
if (p->error[0])
break;
@ -799,6 +852,7 @@ cleanup:
else
ralloc_free(p->error);
FREE(c.last_use);
FREE(c.ureg_map);
FREE(p);