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broadcom/compiler: don't use imprecise_32bit_lowering for idiv lowering

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This is known to produce bogus results for certain combinations of
operands, so don't use it. See this issue for details:

https://gitlab.freedesktop.org/mesa/mesa/-/issues/6555

With this change, the idiv lowering will produce mul_high instructions,
so we need to instruct the compiler to lower those with the ALU lowering
right after the idiv lowering by adding the lower_mul_high option (we
only need to add this to V3D, since V3DV already had it set). This will
cause injection of uadd_carry instructions, for which we have backend
implementations that produce better code for us than the NIR lowering.

total instructions in shared programs: 12457692 -> 12463625 (0.05%)
instructions in affected programs: 23115 -> 29048 (25.67%)
helped: 0
HURT: 111

total threads in shared programs: 416372 -> 416368 (<.01%)
threads in affected programs: 8 -> 4 (-50.00%)
helped: 0
HURT: 2

total uniforms in shared programs: 3704067 -> 3704589 (0.01%)
uniforms in affected programs: 5804 -> 6326 (8.99%)
helped: 2
HURT: 109

total max-temps in shared programs: 2147845 -> 2148088 (0.01%)
max-temps in affected programs: 2456 -> 2699 (9.89%)
helped: 6
HURT: 91

Reviewed-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17871>
This commit is contained in:
Iago Toral Quiroga 2022-08-03 10:44:45 +02:00 • committed by Marge Bot
parent 0c1801706e
commit 73e8fc3efb
2 changed files with 2 additions and 1 deletions
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2
src/broadcom/compiler/vir.c
View file

@ -1563,10 +1563,10 @@ v3d_attempt_compile(struct v3d_compile *c)
NIR_PASS(_, c->s, v3d_nir_lower_txf_ms, c);
NIR_PASS(_, c->s, v3d_nir_lower_image_load_store);
nir_lower_idiv_options idiv_options = {
.imprecise_32bit_lowering = true,
.allow_fp16 = true,
};
NIR_PASS(_, c->s, nir_lower_idiv, &idiv_options);
NIR_PASS(_, c->s, nir_lower_alu);
if (c->key->robust_buffer_access) {
/* v3d_nir_lower_robust_buffer_access assumes constant buffer

1
src/gallium/drivers/v3d/v3d_screen.c
View file

@ -732,6 +732,7 @@ static const nir_shader_compiler_options v3d_nir_options = {
.lower_int64_options = nir_lower_imul_2x32_64,
.has_fsub = true,
.has_isub = true,
.lower_mul_high = true,
.divergence_analysis_options =
nir_divergence_multiple_workgroup_per_compute_subgroup,
/* This will enable loop unrolling in the state tracker so we won't