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54 lines
1.7 KiB
C
54 lines
1.7 KiB
C
/*
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* Copyright 2023 Alyssa Rosenzweig
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* SPDX-License-Identifier: MIT
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*/
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#include "compiler/shader_enums.h"
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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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#include "nir_builder_opcodes.h"
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#include "nir_intrinsics_indices.h"
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/*
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* If a fragment shader reads the layer ID but the vertex shader does not write
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* the layer ID, the fragment shader is supposed to read zero. However, in our
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* hardware, if the vertex shader does not write the layer ID, the value read by
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* the fragment shader is UNDEFINED. To reconcile, the driver passes in whether
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* the layer ID value is written, and this pass predicates layer ID on that
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* system value. This handles both cases without shader variants, at the cost of
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* a single instruction.
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*/
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static bool
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lower(nir_builder *b, nir_intrinsic_instr *intr, void *_)
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{
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if (intr->intrinsic != nir_intrinsic_load_input)
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return false;
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if (nir_intrinsic_io_semantics(intr).location != VARYING_SLOT_LAYER)
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return false;
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b->cursor = nir_after_instr(&intr->instr);
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nir_def *written = nir_load_layer_id_written_agx(b);
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/* Zero extend the mask since layer IDs are 16-bits, so upper bits of the
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* layer ID are necessarily zero.
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*/
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nir_def *mask = nir_u2uN(b, written, intr->def.bit_size);
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nir_def *repl = nir_iand(b, &intr->def, mask);
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nir_def_rewrite_uses_after(&intr->def, repl, repl->parent_instr);
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return true;
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}
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void
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agx_nir_predicate_layer_id(nir_shader *shader)
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{
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assert(shader->info.stage == MESA_SHADER_FRAGMENT);
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/* If layer is not read, there's nothing to lower */
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if (shader->info.inputs_read & VARYING_BIT_LAYER) {
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nir_shader_intrinsics_pass(
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shader, lower, nir_metadata_block_index | nir_metadata_dominance,
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NULL);
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}
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}
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