Mesa (master): i965: Perform basic optimizations on the FIND_LIVE_CHANNEL opcode.
Francisco Jerez
currojerez at kemper.freedesktop.org
Mon May 4 15:40:22 UTC 2015
Module: Mesa
Branch: master
Commit: 3da9f708d4f1375d674fae4d6c6eb06e4c8d9613
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=3da9f708d4f1375d674fae4d6c6eb06e4c8d9613
Author: Francisco Jerez <currojerez at riseup.net>
Date: Fri Feb 20 20:25:04 2015 +0200
i965: Perform basic optimizations on the FIND_LIVE_CHANNEL opcode.
v2: Save some CPU cycles by doing 'return progress' rather than
'depth++' in the discard jump special case.
Reviewed-by: Matt Turner <mattst88 at gmail.com>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
---
src/mesa/drivers/dri/i965/brw_fs.cpp | 48 ++++++++++++++++++++++++++++
src/mesa/drivers/dri/i965/brw_fs.h | 1 +
src/mesa/drivers/dri/i965/brw_fs_cse.cpp | 1 +
src/mesa/drivers/dri/i965/brw_vec4.cpp | 41 ++++++++++++++++++++++++
src/mesa/drivers/dri/i965/brw_vec4.h | 1 +
src/mesa/drivers/dri/i965/brw_vec4_cse.cpp | 1 +
6 files changed, 93 insertions(+)
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 182c79f..1ca7ca6 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -2980,6 +2980,53 @@ fs_visitor::compute_to_mrf()
}
/**
+ * Eliminate FIND_LIVE_CHANNEL instructions occurring outside any control
+ * flow. We could probably do better here with some form of divergence
+ * analysis.
+ */
+bool
+fs_visitor::eliminate_find_live_channel()
+{
+ bool progress = false;
+ unsigned depth = 0;
+
+ foreach_block_and_inst_safe(block, fs_inst, inst, cfg) {
+ switch (inst->opcode) {
+ case BRW_OPCODE_IF:
+ case BRW_OPCODE_DO:
+ depth++;
+ break;
+
+ case BRW_OPCODE_ENDIF:
+ case BRW_OPCODE_WHILE:
+ depth--;
+ break;
+
+ case FS_OPCODE_DISCARD_JUMP:
+ /* This can potentially make control flow non-uniform until the end
+ * of the program.
+ */
+ return progress;
+
+ case SHADER_OPCODE_FIND_LIVE_CHANNEL:
+ if (depth == 0) {
+ inst->opcode = BRW_OPCODE_MOV;
+ inst->src[0] = fs_reg(0);
+ inst->sources = 1;
+ inst->force_writemask_all = true;
+ progress = true;
+ }
+ break;
+
+ default:
+ break;
+ }
+ }
+
+ return progress;
+}
+
+/**
* Once we've generated code, try to convert normal FS_OPCODE_FB_WRITE
* instructions to FS_OPCODE_REP_FB_WRITE.
*/
@@ -3920,6 +3967,7 @@ fs_visitor::optimize()
OPT(opt_zero_samples);
OPT(register_coalesce);
OPT(compute_to_mrf);
+ OPT(eliminate_find_live_channel);
OPT(compact_virtual_grfs);
} while (progress);
diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h
index 0783754..5f4ff15 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.h
+++ b/src/mesa/drivers/dri/i965/brw_fs.h
@@ -239,6 +239,7 @@ public:
bool opt_register_renaming();
bool register_coalesce();
bool compute_to_mrf();
+ bool eliminate_find_live_channel();
bool dead_code_eliminate();
bool remove_duplicate_mrf_writes();
diff --git a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
index 8958e62..43370cb 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
@@ -89,6 +89,7 @@ is_expression(const fs_inst *const inst)
case FS_OPCODE_VARYING_PULL_CONSTANT_LOAD:
case FS_OPCODE_CINTERP:
case FS_OPCODE_LINTERP:
+ case SHADER_OPCODE_FIND_LIVE_CHANNEL:
case SHADER_OPCODE_BROADCAST:
return true;
case SHADER_OPCODE_RCP:
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index 607129b..a8d0e4a 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -1132,6 +1132,46 @@ vec4_visitor::opt_register_coalesce()
}
/**
+ * Eliminate FIND_LIVE_CHANNEL instructions occurring outside any control
+ * flow. We could probably do better here with some form of divergence
+ * analysis.
+ */
+bool
+vec4_visitor::eliminate_find_live_channel()
+{
+ bool progress = false;
+ unsigned depth = 0;
+
+ foreach_block_and_inst_safe(block, vec4_instruction, inst, cfg) {
+ switch (inst->opcode) {
+ case BRW_OPCODE_IF:
+ case BRW_OPCODE_DO:
+ depth++;
+ break;
+
+ case BRW_OPCODE_ENDIF:
+ case BRW_OPCODE_WHILE:
+ depth--;
+ break;
+
+ case SHADER_OPCODE_FIND_LIVE_CHANNEL:
+ if (depth == 0) {
+ inst->opcode = BRW_OPCODE_MOV;
+ inst->src[0] = src_reg(0);
+ inst->force_writemask_all = true;
+ progress = true;
+ }
+ break;
+
+ default:
+ break;
+ }
+ }
+
+ return progress;
+}
+
+/**
* Splits virtual GRFs requesting more than one contiguous physical register.
*
* We initially create large virtual GRFs for temporary structures, arrays,
@@ -1759,6 +1799,7 @@ vec4_visitor::run()
OPT(opt_cse);
OPT(opt_algebraic);
OPT(opt_register_coalesce);
+ OPT(eliminate_find_live_channel);
} while (progress);
pass_num = 0;
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.h b/src/mesa/drivers/dri/i965/brw_vec4.h
index 1f1f100..3f56c5c 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.h
+++ b/src/mesa/drivers/dri/i965/brw_vec4.h
@@ -209,6 +209,7 @@ public:
bool opt_cse();
bool opt_algebraic();
bool opt_register_coalesce();
+ bool eliminate_find_live_channel();
bool is_dep_ctrl_unsafe(const vec4_instruction *inst);
void opt_set_dependency_control();
void opt_schedule_instructions();
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp b/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp
index 66b531c..9147c3c 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_cse.cpp
@@ -72,6 +72,7 @@ is_expression(const vec4_instruction *const inst)
case BRW_OPCODE_MAD:
case BRW_OPCODE_LRP:
case VEC4_OPCODE_UNPACK_UNIFORM:
+ case SHADER_OPCODE_FIND_LIVE_CHANNEL:
case SHADER_OPCODE_BROADCAST:
return true;
case SHADER_OPCODE_RCP:
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