mirror of https://gitlab.freedesktop.org/mesa/mesa
130 lines
4.1 KiB
C
130 lines
4.1 KiB
C
/*
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* Copyright 2023 Alyssa Rosenzweig
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* Copyright 2021 Intel Corporation
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* SPDX-License-Identifier: MIT
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*/
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#include "agx_tilebuffer.h"
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#include "nir.h"
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#include "nir_builder.h"
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/*
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* Lower alpha-to-coverage to sample_mask and some math. May run on either a
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* monolithic pixel shader or a fragment epilogue.
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*/
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bool
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agx_nir_lower_alpha_to_coverage(nir_shader *shader, uint8_t nr_samples)
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{
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/* nir_lower_io_to_temporaries ensures that stores are in the last block */
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nir_function_impl *impl = nir_shader_get_entrypoint(shader);
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nir_block *block = nir_impl_last_block(impl);
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/* The store is probably at the end of the block, so search in reverse. */
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nir_intrinsic_instr *store = NULL;
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nir_foreach_instr_reverse(instr, block) {
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if (instr->type != nir_instr_type_intrinsic)
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continue;
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nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
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if (intr->intrinsic != nir_intrinsic_store_output)
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continue;
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nir_io_semantics sem = nir_intrinsic_io_semantics(intr);
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if (sem.location != FRAG_RESULT_DATA0)
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continue;
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if (sem.dual_source_blend_index != 0)
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continue;
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store = intr;
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break;
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}
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/* If render target 0 isn't written, the alpha value input to
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* alpha-to-coverage is undefined. We assume that the alpha would be 1.0,
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* which would effectively disable alpha-to-coverage, skipping the lowering.
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*
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* Similarly, if there are less than 4 components, alpha is undefined.
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*/
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nir_def *rgba = store ? store->src[0].ssa : NULL;
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if (!rgba || rgba->num_components < 4) {
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nir_metadata_preserve(impl, nir_metadata_all);
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return false;
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}
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nir_builder _b = nir_builder_at(nir_before_instr(&store->instr));
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nir_builder *b = &_b;
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/* Calculate a coverage mask (alpha * nr_samples) bits set. The way we do
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* this isn't particularly clever:
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*
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* # of bits = (unsigned int) (alpha * nr_samples)
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* mask = (1 << (# of bits)) - 1
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*/
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nir_def *alpha = nir_channel(b, rgba, 3);
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nir_def *bits = nir_f2u32(b, nir_fmul_imm(b, alpha, nr_samples));
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nir_def *mask =
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nir_iadd_imm(b, nir_ishl(b, nir_imm_intN_t(b, 1, 16), bits), -1);
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/* Discard samples that aren't covered */
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nir_discard_agx(b, nir_inot(b, mask));
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shader->info.fs.uses_discard = true;
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nir_metadata_preserve(impl,
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nir_metadata_dominance | nir_metadata_block_index);
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return true;
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}
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/*
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* Modify the inputs to store_output instructions in a pixel shader when
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* alpha-to-one is used. May run on either a monolithic pixel shader or a
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* fragment epilogue.
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*/
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bool
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agx_nir_lower_alpha_to_one(nir_shader *shader)
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{
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bool progress = false;
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/* nir_lower_io_to_temporaries ensures that stores are in the last block */
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nir_function_impl *impl = nir_shader_get_entrypoint(shader);
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nir_block *block = nir_impl_last_block(impl);
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nir_foreach_instr(instr, block) {
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if (instr->type != nir_instr_type_intrinsic)
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continue;
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nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
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if (intr->intrinsic != nir_intrinsic_store_output)
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continue;
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/* The OpenGL spec is a bit confusing here, but seemingly alpha-to-one
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* applies to all render targets. Piglit
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* ext_framebuffer_multisample-draw-buffers-alpha-to-one checks this.
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*
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* Even more confusingly, it seems to apply to dual-source blending too.
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* ext_framebuffer_multisample-alpha-to-one-dual-src-blend checks this.
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*/
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nir_io_semantics sem = nir_intrinsic_io_semantics(intr);
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if (sem.location < FRAG_RESULT_DATA0)
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continue;
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nir_def *rgba = intr->src[0].ssa;
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if (rgba->num_components < 4)
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continue;
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nir_builder b = nir_builder_at(nir_before_instr(instr));
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nir_def *rgb1 = nir_vector_insert_imm(
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&b, rgba, nir_imm_floatN_t(&b, 1.0, rgba->bit_size), 3);
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nir_src_rewrite(&intr->src[0], rgb1);
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progress = true;
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}
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if (progress) {
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nir_metadata_preserve(impl,
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nir_metadata_block_index | nir_metadata_dominance);
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} else {
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nir_metadata_preserve(impl, nir_metadata_all);
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}
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return progress;
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}
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