For some reason, we occasionally write the flag register with a MOV.NZ
instruction:
add(8) g25<1>F -g6<0,1,0>F g15<8,8,1>F
cmp.l.f0(8) g26<1>D g25<8,8,1>F 0F
mov.nz.f0(8) null g26<8,8,1>D
A MOV.NZ instruction on the result of a CMP is like comparing for
equality with true in C. It's useless. Removing it allows us to
generate:
add.l.f0(8) null -g6<0,1,0>F g15<8,8,1>F
total instructions in shared programs: 5955701 -> 5951657 (-0.07%)
instructions in affected programs: 302910 -> 298866 (-1.34%)
GAINED: 1
LOST: 0
---
.../drivers/dri/i965/brw_fs_cmod_propagation.cpp | 23 ++++++++++++++--
.../drivers/dri/i965/test_fs_cmod_propagation.cpp | 32 ++++++++++++++++++++++
2 files changed, 52 insertions(+), 3 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_fs_cmod_propagation.cpp
b/src/mesa/drivers/dri/i965/brw_fs_cmod_propagation.cpp
index b521350..dd89512 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_cmod_propagation.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_cmod_propagation.cpp
@@ -57,12 +57,20 @@ opt_cmod_propagation_local(fs_visitor *v, bblock_t *block)
foreach_inst_in_block_reverse_safe(fs_inst, inst, block) {
ip--;
- if (inst->opcode != BRW_OPCODE_CMP ||
+ if ((inst->opcode != BRW_OPCODE_CMP &&
+ inst->opcode != BRW_OPCODE_MOV) ||
inst->predicate != BRW_PREDICATE_NONE ||
!inst->dst.is_null() ||
inst->src[0].file != GRF ||
- inst->src[0].abs ||
- !inst->src[1].is_zero())
+ inst->src[0].abs)
+ continue;
+
+ if (inst->opcode == BRW_OPCODE_CMP && !inst->src[1].is_zero())
+ continue;
+
+ if (inst->opcode == BRW_OPCODE_MOV &&
+ (inst->conditional_mod != BRW_CONDITIONAL_NZ ||
+ inst->src[0].negate))
continue;
bool read_flag = false;
@@ -72,6 +80,15 @@ opt_cmod_propagation_local(fs_visitor *v, bblock_t *block)
scan_inst->dst.reg == inst->src[0].reg &&
scan_inst->dst.reg_offset == inst->src[0].reg_offset &&
!scan_inst->is_partial_write()) {
+ if (inst->opcode == BRW_OPCODE_MOV) {
+ if (!scan_inst->writes_flag())
+ break;
+
+ inst->remove(block);
+ progress = true;
+ break;
+ }
+
enum brw_conditional_mod cond =
inst->src[0].negate ? brw_invert_cmod(inst->conditional_mod)
: inst->conditional_mod;
diff --git a/src/mesa/drivers/dri/i965/test_fs_cmod_propagation.cpp
b/src/mesa/drivers/dri/i965/test_fs_cmod_propagation.cpp
index 15f685e..9541597 100644
--- a/src/mesa/drivers/dri/i965/test_fs_cmod_propagation.cpp
+++ b/src/mesa/drivers/dri/i965/test_fs_cmod_propagation.cpp
@@ -343,3 +343,35 @@ TEST_F(cmod_propagation_test, negate)
EXPECT_EQ(BRW_OPCODE_ADD, instruction(block0, 0)->opcode);
EXPECT_EQ(BRW_CONDITIONAL_L, instruction(block0, 0)->conditional_mod);
}
+
+TEST_F(cmod_propagation_test, movnz)
+{
+ fs_reg dest(v, glsl_type::float_type);
+ fs_reg src0(v, glsl_type::float_type);
+ fs_reg src1(v, glsl_type::float_type);
+ v->emit(BRW_OPCODE_CMP, dest, src0, src1)
+ ->conditional_mod = BRW_CONDITIONAL_GE;
+ v->emit(BRW_OPCODE_MOV, v->reg_null_f, dest)
+ ->conditional_mod = BRW_CONDITIONAL_NZ;
+
+ /* = Before =
+ *
+ * 0: cmp.ge.f0(8) dest src0 src1
+ * 1: mov.nz.f0(8) null dest
+ *
+ * = After =
+ * 0: cmp.ge.f0(8) dest src0 src1
+ */
+
+ v->calculate_cfg();
+ bblock_t *block0 = v->cfg->blocks[0];
+
+ EXPECT_EQ(0, block0->start_ip);
+ EXPECT_EQ(1, block0->end_ip);
+
+ EXPECT_TRUE(cmod_propagation(v));
+ EXPECT_EQ(0, block0->start_ip);
+ EXPECT_EQ(0, block0->end_ip);
+ EXPECT_EQ(BRW_OPCODE_CMP, instruction(block0, 0)->opcode);
+ EXPECT_EQ(BRW_CONDITIONAL_GE, instruction(block0, 0)->conditional_mod);
+}
--
2.0.4
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