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nir: lower load_helper to is_helper if the shader uses demote()

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load_helper_invocation is an Input Builtin, for which the
value should not change during the execution of a shader.
This new pass inserts an is_helper intrinsic before any
demote() instruction and re-uses its value.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9058>
This commit is contained in:
Daniel Schürmann 2021-02-15 16:02:39 +01:00 • committed by Marge Bot
parent 3c31364f5e
commit b689a65316
1 changed files with 62 additions and 0 deletions
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62
src/compiler/nir/nir_lower_discard_or_demote.c
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@ -69,6 +69,56 @@ nir_lower_demote_to_discard_instr(nir_builder *b, nir_instr *instr, void *data)
}
}
static nir_ssa_def *
insert_is_helper(nir_builder *b, nir_instr *instr)
{
/* find best place to insert is_helper */
nir_cf_node *node = &instr->block->cf_node;
while (node->parent->type != nir_cf_node_function)
node = nir_cf_node_prev(node->parent);
nir_block *block = nir_cf_node_as_block(node);
if (block == instr->block) {
b->cursor = nir_before_instr(instr);
} else {
b->cursor = nir_after_block_before_jump(block);
}
return nir_is_helper_invocation(b, 1);
}
static bool
nir_lower_load_helper_to_is_helper(nir_builder *b, nir_instr *instr, void *data)
{
if (instr->type != nir_instr_type_intrinsic)
return false;
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
nir_ssa_def *is_helper = *(nir_ssa_def**) data;
switch (intrin->intrinsic) {
case nir_intrinsic_demote:
case nir_intrinsic_demote_if:
/* insert is_helper at last top level occasion */
if (is_helper == NULL) {
is_helper = insert_is_helper(b, instr);
*(nir_ssa_def**)data = is_helper;
return true;
} else {
return false;
}
case nir_intrinsic_load_helper_invocation:
/* Don't update data: as long as we didn't encounter any demote(),
* we can insert new is_helper() intrinsics. These are placed at
* top-level blocks to ensure correct behavior w.r.t. loops */
if (is_helper == NULL)
is_helper = insert_is_helper(b, instr);
nir_ssa_def_rewrite_uses_ssa(&intrin->dest.ssa, is_helper);
nir_instr_remove_v(instr);
return true;
default:
return false;
}
}
/**
* Optimize discard and demote opcodes.
*
@ -119,6 +169,18 @@ nir_lower_discard_or_demote(nir_shader *shader,
nir_metadata_all,
NULL);
shader->info.fs.uses_demote = false;
} else if (shader->info.fs.uses_demote &&
BITSET_TEST(shader->info.system_values_read,
nir_system_value_from_intrinsic(nir_intrinsic_load_helper_invocation))) {
/* load_helper needs to preserve the value (whether an invocation is
* a helper lane) from the beginning of the shader. */
nir_ssa_def *is_helper = NULL;
progress = nir_shader_instructions_pass(shader,
nir_lower_load_helper_to_is_helper,
nir_metadata_all,
&is_helper);
BITSET_CLEAR(shader->info.system_values_read,
nir_system_value_from_intrinsic(nir_intrinsic_load_helper_invocation));
}
/* Validate again that if uses_demote is set, uses_discard is also be set. */