mirror of https://gitlab.freedesktop.org/mesa/mesa
78 lines
2.6 KiB
C
78 lines
2.6 KiB
C
/*
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* Copyright 2022 Alyssa Rosenzweig
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* SPDX-License-Identifier: MIT
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*/
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#include "compiler/nir/nir.h"
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#include "compiler/nir/nir_builder.h"
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#include "agx_compiler.h"
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/* Fragment shaders with side effects require special handling to ensure the
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* side effects execute as intended. By default, they require late depth
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* testing, to ensure the side effects happen even for killed pixels. To handle,
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* the driver inserts a dummy `gl_FragDepth = gl_Position.z` in shaders that
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* don't otherwise write their depth, forcing a late depth test.
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*
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* For side effects with force early testing forced, the sample mask is written
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* at the *beginning* of the shader (TODO: handle).
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*/
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static bool
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pass(struct nir_builder *b, nir_instr *instr, void *data)
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{
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if (instr->type != nir_instr_type_intrinsic)
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return false;
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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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return false;
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/* Only lower once */
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bool *done = data;
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if (*done)
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return false;
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*done = true;
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b->cursor = nir_before_instr(instr);
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nir_ssa_def *zero = nir_imm_int(b, 0);
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nir_ssa_def *pixel = nir_load_barycentric_pixel(b, 32, .interp_mode = 1);
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nir_ssa_def *position =
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nir_load_interpolated_input(b, 1, 32, pixel, zero, .component = 2 /* Z */,
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.dest_type = nir_type_float32,
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.io_semantics = {
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.location = VARYING_SLOT_POS,
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.num_slots = 1,
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});
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nir_store_output(
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b, position, zero, .io_semantics.location = FRAG_RESULT_DEPTH,
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.write_mask = BITFIELD_MASK(1), .src_type = nir_type_float32);
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b->shader->info.inputs_read |= BITFIELD64_BIT(VARYING_SLOT_POS);
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b->shader->info.outputs_written |= BITFIELD64_BIT(FRAG_RESULT_DEPTH);
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return true;
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}
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bool
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agx_nir_lower_frag_sidefx(nir_shader *s)
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{
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assert(s->info.stage == MESA_SHADER_FRAGMENT);
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/* If there are no side effects, there's nothing to lower */
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if (!s->info.writes_memory)
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return false;
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/* Lower writes from helper invocations with the common pass */
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NIR_PASS_V(s, nir_lower_helper_writes, false);
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/* If depth/stencil feedback is already used, we're done */
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if (s->info.outputs_written & (BITFIELD64_BIT(FRAG_RESULT_STENCIL) |
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BITFIELD64_BIT(FRAG_RESULT_DEPTH)))
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return false;
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bool done = false;
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return nir_shader_instructions_pass(
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s, pass, nir_metadata_block_index | nir_metadata_dominance, &done);
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}
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