[Mesa-dev] [PATCH v2] i965/vec4: track and use independently each flag channel
Alejandro Piñeiro
apinheiro at igalia.com
Mon Oct 19 10:38:41 PDT 2015
vec4_live_variables tracks now each flag channel independently, so
vec4_dead_code_eliminate can update the writemask of null registers,
based on which component are alive at the moment. This would allow
vec4_cmod_propagation to optimize out several movs involving null
registers.
v2: added support to track each flag channel independently at vec4
live_variables, as v1 assumed that it was already doing it, as
pointed by Francisco Jerez
---
I was tempted to split this commit in two, one for tracking each
channel independently at vec4_live_variables, and other for using it
at vec4_dead_code_eliminate, but in the end I concluded that made more
sense as one commit, as are changes tightly tied.
FWIW, the shader-db numbers for the optimization patch ("i965/vec4:
adding vec4_cmod_propagation optimization", 2/5) changed, being now
the following:
total instructions in shared programs: 6240413 -> 6235841 (-0.07%)
instructions in affected programs: 401933 -> 397361 (-1.14%)
total loops in shared programs: 1979 -> 1979 (0.00%)
helped: 2265
HURT: 0
That are slightly worse that the numbers for the first version of the
patch, before adding that extra check. I will use this numbers if this
patch is approved.
FWIW, without this change on live_variables and dead_code eliminate,
the numbers on the optimization would be the following ones:
total instructions in shared programs: 6240413 -> 6240253 (-0.00%)
instructions in affected programs: 18965 -> 18805 (-0.84%)
total loops in shared programs: 1979 -> 1979 (0.00%)
helped: 160
HURT:
src/mesa/drivers/dri/i965/brw_ir_vec4.h | 26 ++++++++++++++++++
.../dri/i965/brw_vec4_dead_code_eliminate.cpp | 31 +++++++++++++++-------
.../drivers/dri/i965/brw_vec4_live_variables.cpp | 14 ++++++----
3 files changed, 57 insertions(+), 14 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_ir_vec4.h b/src/mesa/drivers/dri/i965/brw_ir_vec4.h
index 96dd633..934d7b1 100644
--- a/src/mesa/drivers/dri/i965/brw_ir_vec4.h
+++ b/src/mesa/drivers/dri/i965/brw_ir_vec4.h
@@ -185,6 +185,32 @@ public:
return predicate || opcode == VS_OPCODE_UNPACK_FLAGS_SIMD4X2;
}
+ bool reads_flag(unsigned c)
+ {
+ if (!reads_flag())
+ return false;
+
+ switch(predicate) {
+ case BRW_PREDICATE_NONE:
+ return false;
+ break;
+ case BRW_PREDICATE_ALIGN16_REPLICATE_X:
+ return (c == 0 ? true : false);
+ break;
+ case BRW_PREDICATE_ALIGN16_REPLICATE_Y:
+ return (c == 1 ? true : false);
+ break;
+ case BRW_PREDICATE_ALIGN16_REPLICATE_Z:
+ return (c == 2 ? true : false);
+ break;
+ case BRW_PREDICATE_ALIGN16_REPLICATE_W:
+ return (c == 3 ? true : false);
+ break;
+ default:
+ return true;
+ }
+ }
+
bool writes_flag()
{
return (conditional_mod && (opcode != BRW_OPCODE_SEL &&
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp b/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp
index 8fc7a36..d4216fd 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp
@@ -78,13 +78,19 @@ vec4_visitor::dead_code_eliminate()
sizeof(BITSET_WORD));
foreach_inst_in_block_reverse(vec4_instruction, inst, block) {
- if (inst->dst.file == GRF && !inst->has_side_effects()) {
+ if ((inst->dst.file == GRF && !inst->has_side_effects()) ||
+ (inst->dst.is_null() && inst->writes_flag())){
bool result_live[4] = { false };
- for (unsigned i = 0; i < inst->regs_written; i++) {
- for (int c = 0; c < 4; c++)
- result_live[c] |= BITSET_TEST(
- live, var_from_reg(alloc, offset(inst->dst, i), c));
+ if (inst->dst.file == GRF) {
+ for (unsigned i = 0; i < inst->regs_written; i++) {
+ for (int c = 0; c < 4; c++)
+ result_live[c] |= BITSET_TEST(
+ live, var_from_reg(alloc, offset(inst->dst, i), c));
+ }
+ } else {
+ for (unsigned c = 0; c < 4; c++)
+ result_live[c] = BITSET_TEST(flag_live, c);
}
/* If the instruction can't do writemasking, then it's all or
@@ -117,7 +123,11 @@ vec4_visitor::dead_code_eliminate()
}
if (inst->dst.is_null() && inst->writes_flag()) {
- if (!BITSET_TEST(flag_live, 0)) {
+ bool combined_live = false;
+ for (unsigned c = 0; c < 4; c++)
+ combined_live |= BITSET_TEST(flag_live,c);
+
+ if (!combined_live) {
inst->opcode = BRW_OPCODE_NOP;
progress = true;
continue;
@@ -136,7 +146,8 @@ vec4_visitor::dead_code_eliminate()
}
if (inst->writes_flag()) {
- BITSET_CLEAR(flag_live, 0);
+ for (unsigned c = 0; c < 4; c++)
+ BITSET_CLEAR(flag_live, c);
}
for (int i = 0; i < 3; i++) {
@@ -150,8 +161,10 @@ vec4_visitor::dead_code_eliminate()
}
}
- if (inst->reads_flag()) {
- BITSET_SET(flag_live, 0);
+ for (unsigned c = 0; c < 4; c++) {
+ if (inst->reads_flag(c)) {
+ BITSET_SET(flag_live, c);
+ }
}
}
}
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_live_variables.cpp b/src/mesa/drivers/dri/i965/brw_vec4_live_variables.cpp
index 6782379..aa9a657 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_live_variables.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_live_variables.cpp
@@ -86,9 +86,10 @@ vec4_live_variables::setup_def_use()
}
}
}
- if (inst->reads_flag()) {
- if (!BITSET_TEST(bd->flag_def, 0)) {
- BITSET_SET(bd->flag_use, 0);
+ for (unsigned c = 0; c < 4; c++) {
+ if (inst->reads_flag(c) &&
+ !BITSET_TEST(bd->flag_def, c)) {
+ BITSET_SET(bd->flag_use, c);
}
}
@@ -110,8 +111,11 @@ vec4_live_variables::setup_def_use()
}
}
if (inst->writes_flag()) {
- if (!BITSET_TEST(bd->flag_use, 0)) {
- BITSET_SET(bd->flag_def, 0);
+ for (unsigned c = 0; c < 4; c++) {
+ if ((inst->dst.writemask & (1 << c)) &&
+ !BITSET_TEST(bd->flag_use, c)) {
+ BITSET_SET(bd->flag_def, c);
+ }
}
}
--
2.1.4
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