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nir,zink: Make lower_discard_if a common pass 

This pass (lowering discard_if to control flow and unconditional
discard) was originally written for Zink, but is useful for hardware
that lacks conditional discard instructions like AGX. In theory AGX
could implement a conditional discard with CSEL, but the vendor
compiler uses a lowering like this one. Since I like not writing code,
I'd like to use the pass that's already in tree.

v2: Don't preserve dominance (Jason). Assert we don't see demotes or
terminates (Jason). Add Mike's ack.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Acked-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14217>
This commit is contained in:
Alyssa Rosenzweig 2021-12-14 15:59:45 -05:00 committed by Marge Bot
parent 538356e3e6
commit aaf00a1b4d
4 changed files with 107 additions and 74 deletions
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1
src/compiler/nir/meson.build
View File

@ -143,6 +143,7 @@ files_libnir = files(
'nir_lower_clip_halfz.c',
'nir_lower_convert_alu_types.c',
'nir_lower_variable_initializers.c',
'nir_lower_discard_if.c',
'nir_lower_discard_or_demote.c',
'nir_lower_double_ops.c',
'nir_lower_drawpixels.c',

2
src/compiler/nir/nir.h
View File

@ -5137,6 +5137,8 @@ typedef enum {
bool nir_lower_interpolation(nir_shader *shader,
nir_lower_interpolation_options options);
bool nir_lower_discard_if(nir_shader *shader);
bool nir_lower_discard_or_demote(nir_shader *shader,
bool force_correct_quad_ops_after_discard);

103
src/compiler/nir/nir_lower_discard_if.c Normal file
View File

@ -0,0 +1,103 @@
/*
* Copyright 2018 Collabora Ltd.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* on the rights to use, copy, modify, merge, publish, distribute, sub
* license, and/or sell copies of the Software, and to permit persons to whom
* the Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
* THE AUTHOR(S) AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
* USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include "nir.h"
#include "compiler/nir/nir_builder.h"
static bool
lower_discard_if_instr(nir_builder *b, nir_instr *instr_, UNUSED void *cb_data)
{
if (instr_->type != nir_instr_type_intrinsic)
return false;
nir_intrinsic_instr *instr = nir_instr_as_intrinsic(instr_);
if (instr->intrinsic == nir_intrinsic_discard_if) {
b->cursor = nir_before_instr(&instr->instr);
nir_if *if_stmt = nir_push_if(b, nir_ssa_for_src(b, instr->src[0], 1));
nir_discard(b);
nir_pop_if(b, if_stmt);
nir_instr_remove(&instr->instr);
return true;
} else if (instr->intrinsic == nir_intrinsic_terminate_if ||
instr->intrinsic == nir_intrinsic_demote_if) {
unreachable("todo: handle terminates and demotes for Vulkan");
}
/* a shader like this (shaders@glsl-fs-discard-04):
uniform int j, k;
void main()
{
for (int i = 0; i < j; i++) {
if (i > k)
continue;
discard;
}
gl_FragColor = vec4(0.0, 1.0, 0.0, 0.0);
}
will generate nir like:
loop {
//snip
if ssa_11 {
block block_5:
/ preds: block_4 /
vec1 32 ssa_17 = iadd ssa_50, ssa_31
/ succs: block_7 /
} else {
block block_6:
/ preds: block_4 /
intrinsic discard () () <-- not last instruction
vec1 32 ssa_23 = iadd ssa_50, ssa_31 <-- dead code loop itr increment
/ succs: block_7 /
}
//snip
}
which means that we can't assert like this:
assert(instr->intrinsic != nir_intrinsic_discard ||
nir_block_last_instr(instr->instr.block) == &instr->instr);
and it's unnecessary anyway since later optimizations will dce the
instructions following the discard
*/
return false;
}
bool
nir_lower_discard_if(nir_shader *shader)
{
return nir_shader_instructions_pass(shader,
lower_discard_if_instr,
nir_metadata_none,
NULL);
}

75
src/gallium/drivers/zink/zink_compiler.c
View File

@ -75,79 +75,6 @@ reads_work_dim(nir_shader *shader)
return BITSET_TEST(shader->info.system_values_read, SYSTEM_VALUE_WORK_DIM);
}
static bool
lower_discard_if_instr(nir_builder *b, nir_instr *instr_, UNUSED void *cb_data)
{
if (instr_->type != nir_instr_type_intrinsic)
return false;
nir_intrinsic_instr *instr = nir_instr_as_intrinsic(instr_);
if (instr->intrinsic == nir_intrinsic_discard_if) {
b->cursor = nir_before_instr(&instr->instr);
nir_if *if_stmt = nir_push_if(b, nir_ssa_for_src(b, instr->src[0], 1));
nir_discard(b);
nir_pop_if(b, if_stmt);
nir_instr_remove(&instr->instr);
return true;
}
/* a shader like this (shaders@glsl-fs-discard-04):
uniform int j, k;
void main()
{
for (int i = 0; i < j; i++) {
if (i > k)
continue;
discard;
}
gl_FragColor = vec4(0.0, 1.0, 0.0, 0.0);
}
will generate nir like:
loop {
//snip
if ssa_11 {
block block_5:
/ preds: block_4 /
vec1 32 ssa_17 = iadd ssa_50, ssa_31
/ succs: block_7 /
} else {
block block_6:
/ preds: block_4 /
intrinsic discard () () <-- not last instruction
vec1 32 ssa_23 = iadd ssa_50, ssa_31 <-- dead code loop itr increment
/ succs: block_7 /
}
//snip
}
which means that we can't assert like this:
assert(instr->intrinsic != nir_intrinsic_discard ||
nir_block_last_instr(instr->instr.block) == &instr->instr);
and it's unnecessary anyway since post-vtn optimizing will dce the instructions following the discard
*/
return false;
}
static bool
lower_discard_if(nir_shader *shader)
{
return nir_shader_instructions_pass(shader,
lower_discard_if_instr,
nir_metadata_dominance,
NULL);
}
static bool
lower_work_dim_instr(nir_builder *b, nir_instr *in, void *data)
{
@ -1858,7 +1785,7 @@ zink_shader_create(struct zink_screen *screen, struct nir_shader *nir,
optimize_nir(nir);
NIR_PASS_V(nir, nir_remove_dead_variables, nir_var_function_temp, NULL);
NIR_PASS_V(nir, lower_discard_if);
NIR_PASS_V(nir, nir_lower_discard_if);
NIR_PASS_V(nir, nir_lower_fragcolor,
nir->info.fs.color_is_dual_source ? 1 : 8);
NIR_PASS_V(nir, lower_64bit_vertex_attribs);