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jay/register_allocate: set num_regs[MEM] properly

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this is both a correctness fix (insufficient MEM registers reserved in some
cases) and a performance fix (unnecessary allocations & zeroing in the RA when
we don't spill).

fixes dEQP-VK.dgc.ext.compute.misc.scratch_space

stats are noise but positive i guess.

Totals from 35 (1.32% of 2647) affected shaders:
Instrs: 396770 -> 396690 (-0.02%)
CodeSize: 6040832 -> 6039600 (-0.02%)

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41510>
This commit is contained in:
Alyssa Rosenzweig 2026-05-07 14:14:31 -04:00 • committed by Marge Bot
parent d67e37a24c
commit 37e4144693
1 changed files with 35 additions and 36 deletions
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71
src/intel/compiler/jay/jay_register_allocate.c
View file

@ -1424,6 +1424,16 @@ build_partition(jay_shader *shader, unsigned *blocks, unsigned n)
}
}
static unsigned
gpr_limit(jay_shader *shader)
{
/* If testing spilling, set limit tightly. */
bool test = (jay_debug & JAY_DBG_SPILL);
test &= shader->stage != MESA_SHADER_VERTEX;
return test ? 13 : shader->num_regs[GPR];
}
/*
* Partition the register file for the entire shader. All functions must
* share the same partition for correctness with non-uniform function calls.
@ -1543,42 +1553,12 @@ jay_partition_grf(jay_shader *shader)
}
}
/* TODO: Arbitrary. Need to rework somehow, we have options. */
shader->num_regs[MEM] = 512;
}
static bool
spill_gpr(jay_function *f)
{
unsigned limit = f->shader->num_regs[GPR];
/* If testing spilling, set limit tightly. */
if ((jay_debug & JAY_DBG_SPILL) &&
f->shader->stage != MESA_SHADER_VERTEX) {
limit = 13;
/* This should be an acceptable upper limit since we assign memory tightly
* thanks to the usual SSA allocator guarantees.
*/
if (demand[GPR] > gpr_limit(shader)) {
shader->num_regs[MEM] = demand[GPR];
}
if (f->demand[GPR] <= limit) {
return false;
}
/* Spilling requires reserving UGPRs for spilling */
unsigned reservation = f->shader->dispatch_width + 1;
f->shader->num_regs[UGPR] -= reservation;
f->shader->partition.large_ugpr_block.len -= reservation;
jay_spill(f, limit);
jay_validate(f->shader, "spilling");
jay_compute_liveness(f);
jay_calculate_register_demands(f);
if (f->demand[GPR] > limit) {
fprintf(stderr, "limit %u but demand %u\n", limit, f->demand[GPR]);
fflush(stdout);
UNREACHABLE("spiller bug");
}
return true;
}
static void
@ -1588,7 +1568,26 @@ jay_register_allocate_function(jay_function *f)
jay_ra_state ra = { .b.shader = shader, .b.func = f };
/* Spill as needed to fit within the limits. */
bool spilled = spill_gpr(f);
unsigned limit = gpr_limit(f->shader);
bool spilled = f->demand[GPR] > limit;
if (spilled) {
/* Spilling requires reserving UGPRs for spilling */
unsigned reservation = f->shader->dispatch_width + 1;
f->shader->num_regs[UGPR] -= reservation;
f->shader->partition.large_ugpr_block.len -= reservation;
jay_spill(f, limit);
jay_validate(f->shader, "spilling");
jay_compute_liveness(f);
jay_calculate_register_demands(f);
}
if (f->demand[GPR] > limit) {
fprintf(stderr, "limit %u but demand %u\n", limit, f->demand[GPR]);
fflush(stdout);
UNREACHABLE("spiller bug");
}
/* The spiller/SSA repair does not work on UGPRs because it cannot tolerate
* the critical edges on the physical CFG. Fortunately, dynamic GPR/UGPR