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i915/corm: use utemp for vec texcoord to avoid phase boundaries

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When a vec construction feeds a single-use tex instruction, use a
utemp (unpreserved temp) instead of an R-file temp for the vec dest.
R-file temps written by ALU trigger tex indirect phase boundaries
when read by subsequent texld instructions; utemps do not.

Preserve the utemp allocation across i915_release_utemps so the
value survives until the texld consumer reads it.

shader-db (I915_FS=nir): 249/403 compiled, 3495 alu
shader-db (I915_FS=both): nir won 249 (26 identical, 1 tied, 217 better, 5 only),
  40 TGSI, 114 neither

Assisted-by: Claude
This commit is contained in:
Adam Jackson 2026-05-07 11:25:26 -04:00
parent 800375c3c4
commit 2a2ef36852
1 changed files with 10 additions and 0 deletions
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10
src/gallium/drivers/i915/i915_fpc_nir.c
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@ -523,6 +523,7 @@ emit_alu(struct nir_to_i915 *c, nir_alu_instr *alu)
/* If this vec's only consumer is a store_output, write directly /* If this vec's only consumer is a store_output, write directly
* to the output register instead of going through a temp. * to the output register instead of going through a temp.
* If it's a tex instruction, use a utemp to avoid phase boundaries.
*/ */
if (list_is_singular(&def->uses)) { if (list_is_singular(&def->uses)) {
nir_src *use = list_first_entry(&def->uses, nir_src, use_link); nir_src *use = list_first_entry(&def->uses, nir_src, use_link);
@ -539,6 +540,11 @@ emit_alu(struct nir_to_i915 *c, nir_alu_instr *alu)
dest = out; dest = out;
set_ureg(c, def, dest); set_ureg(c, def, dest);
} }
} else if (use_instr->type == nir_instr_type_tex) {
i915_release_temp(p, GET_UREG_NR(dest));
uint32_t utemp = i915_get_utemp(p);
dest = utemp;
set_ureg(c, def, dest);
} }
} }
@ -757,7 +763,11 @@ emit_alu(struct nir_to_i915 *c, nir_alu_instr *alu)
if (p->csr == pre_csr + 3) if (p->csr == pre_csr + 3)
c->def_csr[def->index] = pre_csr; c->def_csr[def->index] = pre_csr;
uint32_t save = 0;
if (GET_UREG_TYPE(dest) == REG_TYPE_U)
save = p->utemp_flag & (1 << GET_UREG_NR(dest));
i915_release_utemps(p); i915_release_utemps(p);
p->utemp_flag |= save;
} }
static uint32_t static uint32_t