Mesa (main): pan/va: Add pass to insert flow control
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gitlab-mirror at kemper.freedesktop.org
Wed Jun 1 16:29:30 UTC 2022
Module: Mesa
Branch: main
Commit: 7e3b9cf75403ff2cc11238e18db99aa8f0ae9baf
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=7e3b9cf75403ff2cc11238e18db99aa8f0ae9baf
Author: Alyssa Rosenzweig <alyssa at collabora.com>
Date: Thu May 19 16:57:31 2022 -0400
pan/va: Add pass to insert flow control
To set flow control modifiers correctly and efficiently, we need a pass that
runs after register allocation and scheduling, but before packing. Add such a
pass.
Signed-off-by: Alyssa Rosenzweig <alyssa at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16804>
---
src/panfrost/bifrost/compiler.h | 5 ++
src/panfrost/bifrost/meson.build | 1 +
src/panfrost/bifrost/valhall/va_compiler.h | 1 +
src/panfrost/bifrost/valhall/va_insert_flow.c | 118 ++++++++++++++++++++++++++
4 files changed, 125 insertions(+)
diff --git a/src/panfrost/bifrost/compiler.h b/src/panfrost/bifrost/compiler.h
index 71d24750d37..7ca480ebc9e 100644
--- a/src/panfrost/bifrost/compiler.h
+++ b/src/panfrost/bifrost/compiler.h
@@ -684,6 +684,11 @@ typedef struct bi_block {
/* Scoreboard state at the start/end of block */
struct bi_scoreboard_state scoreboard_in, scoreboard_out;
+ /* On Valhall, indicates we need a terminal NOP to implement jumps to
+ * the end of the shader.
+ */
+ bool needs_nop;
+
/* Flags available for pass-internal use */
uint8_t pass_flags;
} bi_block;
diff --git a/src/panfrost/bifrost/meson.build b/src/panfrost/bifrost/meson.build
index f0d5a074919..c7dfca551b5 100644
--- a/src/panfrost/bifrost/meson.build
+++ b/src/panfrost/bifrost/meson.build
@@ -46,6 +46,7 @@ libpanfrost_bifrost_files = files(
'bi_validate.c',
'bir.c',
'bifrost_compile.c',
+ 'valhall/va_insert_flow.c',
'valhall/va_lower_constants.c',
'valhall/va_lower_isel.c',
'valhall/va_lower_split_64bit.c',
diff --git a/src/panfrost/bifrost/valhall/va_compiler.h b/src/panfrost/bifrost/valhall/va_compiler.h
index 7605a9da9eb..db913516d12 100644
--- a/src/panfrost/bifrost/valhall/va_compiler.h
+++ b/src/panfrost/bifrost/valhall/va_compiler.h
@@ -40,6 +40,7 @@ void va_repair_fau(bi_builder *b, bi_instr *I);
void va_fuse_add_imm(bi_instr *I);
void va_lower_constants(bi_context *ctx, bi_instr *I);
void va_lower_isel(bi_instr *I);
+void va_insert_flow_control_nops(bi_context *ctx);
uint64_t va_pack_instr(const bi_instr *I);
static inline unsigned
diff --git a/src/panfrost/bifrost/valhall/va_insert_flow.c b/src/panfrost/bifrost/valhall/va_insert_flow.c
new file mode 100644
index 00000000000..4bb2c4a7d60
--- /dev/null
+++ b/src/panfrost/bifrost/valhall/va_insert_flow.c
@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2022 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
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * 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 NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS 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 "va_compiler.h"
+#include "valhall_enums.h"
+#include "bi_builder.h"
+
+/*
+ * Insert flow control into a scheduled and register allocated shader. This
+ * pass runs after scheduling and register allocation. This pass only
+ * inserts NOPs with the appropriate flow control modifiers. It should be
+ * followed by a cleanup pass to merge flow control modifiers on adjacent
+ * instructions, eliminating the NOPs. This decouples optimization from
+ * correctness, simplifying both passes.
+ */
+
+/*
+ * Insert a NOP instruction with given flow control.
+ */
+static void
+bi_flow(bi_context *ctx, bi_cursor cursor, enum va_flow flow)
+{
+ bi_builder b = bi_init_builder(ctx, cursor);
+
+ bi_nop(&b)->flow = flow;
+}
+
+/*
+ * Determine if execution should terminate after a given block. Execution cannot
+ * terminate within a basic block.
+ */
+static bool
+va_should_end(bi_block *block)
+{
+ /* Don't return if we're succeeded by instructions */
+ for (unsigned i = 0; i < ARRAY_SIZE(block->successors); ++i) {
+ bi_block *succ = block->successors[i];
+
+ if (succ)
+ return false;
+ }
+
+ return true;
+}
+
+/*
+ * Given a program with no flow control modifiers, insert NOPs signaling the
+ * required flow control. Not much optimization happens here.
+ */
+void
+va_insert_flow_control_nops(bi_context *ctx)
+{
+ bi_foreach_block(ctx, block) {
+ bi_foreach_instr_in_block_safe(block, I) {
+ switch (I->op) {
+ /* Signal barriers immediately */
+ case BI_OPCODE_BARRIER:
+ bi_flow(ctx, bi_after_instr(I), VA_FLOW_WAIT);
+ break;
+
+ /* Insert waits for tilebuffer and depth/stencil instructions. These
+ * only happen in regular fragment shaders, as the required waits are
+ * assumed to already have happened in blend shaders.
+ */
+ case BI_OPCODE_BLEND:
+ case BI_OPCODE_LD_TILE:
+ case BI_OPCODE_ST_TILE:
+ if (!ctx->inputs->is_blend)
+ bi_flow(ctx, bi_before_instr(I), VA_FLOW_WAIT);
+ break;
+ case BI_OPCODE_ATEST:
+ case BI_OPCODE_ZS_EMIT:
+ if (!ctx->inputs->is_blend)
+ bi_flow(ctx, bi_before_instr(I), VA_FLOW_WAIT0126);
+ break;
+
+ /* TODO: Optimize waits for asynchronous instructions */
+ default:
+ if (bi_opcode_props[I->op].message)
+ bi_flow(ctx, bi_after_instr(I), VA_FLOW_WAIT0);
+ break;
+ }
+ }
+
+ /* End exeuction at the end of the block if needed, or reconverge if we
+ * continue but we don't need to end execution.
+ */
+ if (va_should_end(block) || block->needs_nop) {
+ /* Don't bother adding a NOP into an unreachable block */
+ if (block == bi_start_block(&ctx->blocks) || bi_num_predecessors(block))
+ bi_flow(ctx, bi_after_block(block), VA_FLOW_END);
+ } else if (bi_reconverge_branches(block)) {
+ /* TODO: Do we have ever need to reconverge from an empty block? */
+ if (!list_is_empty(&block->instructions))
+ bi_flow(ctx, bi_after_block(block), VA_FLOW_RECONVERGE);
+ }
+ }
+}
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