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turnip: Short-circuit if ladder generation for constant index SSBO/UBOs.

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The compiler *can* eventually chew through all the copy prop, constant
folding, and dead_cf necessary to use just our constant index, but we can
save a whole lot of hassle by chasing the MOVs up front and finding the
constant.

dEQP-VK.ubo.3_level_array.scalar.row_major_mat4.both goes from 2.0s to
1.6s on a release build (3.1s to 2.1s for a debug build like we use in CI).

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11613>
This commit is contained in:
Emma Anholt 2021-06-25 14:02:07 -07:00 • committed by Marge Bot
parent 0afab39af9
commit fd5293cc43
1 changed files with 10 additions and 2 deletions
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12
src/freedreno/vulkan/tu_shader.c
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@ -279,7 +279,7 @@ lower_ssbo_ubo_intrinsic(nir_builder *b, nir_intrinsic_instr *intrin)
/* The bindless base is part of the instruction, which means that part of
* the "pointer" has to be constant. We solve this in the same way the blob
* does, by generating a bunch of if-statements. In the usual case where
* the descriptor set is constant this will get optimized out.
* the descriptor set is constant we can skip that, though).
*/
unsigned buffer_src;
@ -290,11 +290,19 @@ lower_ssbo_ubo_intrinsic(nir_builder *b, nir_intrinsic_instr *intrin)
buffer_src = 0;
}
nir_ssa_def *base_idx = nir_channel(b, intrin->src[buffer_src].ssa, 0);
nir_ssa_scalar scalar_idx = nir_ssa_scalar_resolved(intrin->src[buffer_src].ssa, 0);
nir_ssa_def *descriptor_idx = nir_channel(b, intrin->src[buffer_src].ssa, 1);
nir_ssa_def *results[MAX_SETS + 1] = { NULL };
if (nir_ssa_scalar_is_const(scalar_idx)) {
nir_ssa_def *bindless =
nir_bindless_resource_ir3(b, 32, descriptor_idx, .desc_set = nir_ssa_scalar_as_uint(scalar_idx));
nir_instr_rewrite_src_ssa(&intrin->instr, &intrin->src[buffer_src], bindless);
return;
}
nir_ssa_def *base_idx = nir_channel(b, scalar_idx.def, scalar_idx.comp);
for (unsigned i = 0; i < MAX_SETS + 1; i++) {
/* if (base_idx == i) { ... */
nir_if *nif = nir_push_if(b, nir_ieq_imm(b, base_idx, i));