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i965/fs: Propagate cmod across flag read if it contains the same value. 

total instructions in shared programs: 5959463 -> 5958900 (-0.01%)
instructions in affected programs:     70031 -> 69468 (-0.80%)

Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Matt Turner 2015-01-03 12:18:15 -08:00
parent 3fb5b2bc47
commit d6317beb46
2 changed files with 55 additions and 2 deletions
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16
src/mesa/drivers/dri/i965/brw_fs_cmod_propagation.cpp
View File

@ -37,6 +37,15 @@
* we can do the comparison as part of the ADD instruction directly:
*
* add.ge.f0(8) g70<1>F g69<8,8,1>F 4096F
*
* If there had been a use of the flag register and another CMP using g70
*
* add.ge.f0(8) g70<1>F g69<8,8,1>F 4096F
* (+f0) sel(8) g71<F> g72<8,8,1>F g73<8,8,1>F
* cmp.ge.f0(8) null g70<8,8,1>F 0F
*
* we can recognize that the CMP is generating the flag value that already
* exists and therefore remove the instruction.
*/
static bool
@ -57,6 +66,7 @@ opt_cmod_propagation_local(fs_visitor *v, bblock_t *block)
!inst->src[1].is_zero())
continue;
bool read_flag = false;
foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst, inst,
block) {
if (scan_inst->overwrites_reg(inst->src[0])) {
@ -65,7 +75,7 @@ opt_cmod_propagation_local(fs_visitor *v, bblock_t *block)
break;
if (scan_inst->can_do_cmod() &&
(scan_inst->conditional_mod == BRW_CONDITIONAL_NONE ||
((!read_flag && scan_inst->conditional_mod == BRW_CONDITIONAL_NONE) ||
scan_inst->conditional_mod == inst->conditional_mod)) {
scan_inst->conditional_mod = inst->conditional_mod;
inst->remove(block);
@ -74,8 +84,10 @@ opt_cmod_propagation_local(fs_visitor *v, bblock_t *block)
break;
}
if (scan_inst->reads_flag() || scan_inst->writes_flag())
if (scan_inst->writes_flag())
break;
read_flag = read_flag || scan_inst->reads_flag();
}
}

41
src/mesa/drivers/dri/i965/test_fs_cmod_propagation.cpp
View File

@ -309,3 +309,44 @@ TEST_F(cmod_propagation_test, intervening_dest_write)
EXPECT_EQ(BRW_OPCODE_CMP, instruction(block0, 2)->opcode);
EXPECT_EQ(BRW_CONDITIONAL_GE, instruction(block0, 2)->conditional_mod);
}
TEST_F(cmod_propagation_test, intervening_flag_read_same_value)
{
fs_reg dest0 = v->vgrf(glsl_type::float_type);
fs_reg dest1 = v->vgrf(glsl_type::float_type);
fs_reg src0 = v->vgrf(glsl_type::float_type);
fs_reg src1 = v->vgrf(glsl_type::float_type);
fs_reg src2 = v->vgrf(glsl_type::float_type);
fs_reg zero(0.0f);
v->emit(BRW_OPCODE_ADD, dest0, src0, src1)
->conditional_mod = BRW_CONDITIONAL_GE;
v->emit(BRW_OPCODE_SEL, dest1, src2, zero)
->predicate = BRW_PREDICATE_NORMAL;
v->emit(BRW_OPCODE_CMP, v->reg_null_f, dest0, zero)
->conditional_mod = BRW_CONDITIONAL_GE;
/* = Before =
*
* 0: add.ge.f0(8) dest0 src0 src1
* 1: (+f0) sel(8) dest1 src2 0.0f
* 2: cmp.ge.f0(8) null dest0 0.0f
*
* = After =
* 0: add.ge.f0(8) dest0 src0 src1
* 1: (+f0) sel(8) dest1 src2 0.0f
*/
v->calculate_cfg();
bblock_t *block0 = v->cfg->blocks[0];
EXPECT_EQ(0, block0->start_ip);
EXPECT_EQ(2, block0->end_ip);
EXPECT_TRUE(cmod_propagation(v));
EXPECT_EQ(0, block0->start_ip);
EXPECT_EQ(1, block0->end_ip);
EXPECT_EQ(BRW_OPCODE_ADD, instruction(block0, 0)->opcode);
EXPECT_EQ(BRW_CONDITIONAL_GE, instruction(block0, 0)->conditional_mod);
EXPECT_EQ(BRW_OPCODE_SEL, instruction(block0, 1)->opcode);
EXPECT_EQ(BRW_PREDICATE_NORMAL, instruction(block0, 1)->predicate);
}