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v3d: Dead-code eliminate unused flags updates.

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The greedy comparison folding in bcsel means that we may have left the
original bool-generating NIR ALU instruction dead, but DCE wasn't
eliminating the VIR code for it because of the flags updates.

total instructions in shared programs: 5186024 -> 5100894 (-1.64%)
instructions in affected programs: 1448695 -> 1363565 (-5.88%)
This commit is contained in:
Eric Anholt
2018-12-29 12:44:22 -08:00
parent 20e3526298
commit b36757448d
1 changed files with 42 additions and 4 deletions
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src/broadcom/compiler/vir_opt_dead_code.c
+42 -4
View File
@@ -92,6 +92,24 @@ can_write_to_null(struct v3d_compile *c, struct qinst *inst)
return true;
}
static void
vir_dce_flags(struct v3d_compile *c, struct qinst *inst)
{
if (debug) {
fprintf(stderr,
"Removing flags write from: ");
vir_dump_inst(c, inst);
fprintf(stderr, "\n");
}
assert(inst->qpu.type == V3D_QPU_INSTR_TYPE_ALU);
inst->qpu.flags.apf = V3D_QPU_PF_NONE;
inst->qpu.flags.mpf = V3D_QPU_PF_NONE;
inst->qpu.flags.auf = V3D_QPU_UF_NONE;
inst->qpu.flags.muf = V3D_QPU_UF_NONE;
}
bool
vir_opt_dead_code(struct v3d_compile *c)
{
@@ -112,7 +130,15 @@ vir_opt_dead_code(struct v3d_compile *c)
}
vir_for_each_block(block, c) {
struct qinst *last_flags_write = NULL;
vir_for_each_inst_safe(inst, block) {
/* If this instruction reads the flags, we can't
* remove the flags generation for it.
*/
if (v3d_qpu_reads_flags(&inst->qpu))
last_flags_write = NULL;
if (inst->dst.file != QFILE_NULL &&
!(inst->dst.file == QFILE_TEMP &&
!used[inst->dst.index])) {
@@ -122,10 +148,21 @@ vir_opt_dead_code(struct v3d_compile *c)
if (vir_has_side_effects(c, inst))
continue;
if (inst->qpu.flags.apf != V3D_QPU_PF_NONE ||
inst->qpu.flags.mpf != V3D_QPU_PF_NONE ||
inst->qpu.flags.auf != V3D_QPU_UF_NONE ||
inst->qpu.flags.muf != V3D_QPU_UF_NONE ||
if (v3d_qpu_writes_flags(&inst->qpu)) {
/* If we obscure a previous flags write,
* drop it.
*/
if (last_flags_write &&
(inst->qpu.flags.apf != V3D_QPU_PF_NONE ||
inst->qpu.flags.mpf != V3D_QPU_PF_NONE)) {
vir_dce_flags(c, last_flags_write);
progress = true;
}
last_flags_write = inst;
}
if (v3d_qpu_writes_flags(&inst->qpu) ||
has_nonremovable_reads(c, inst)) {
/* If we can't remove the instruction, but we
* don't need its destination value, just
@@ -162,6 +199,7 @@ vir_opt_dead_code(struct v3d_compile *c)
}
}
assert(inst != last_flags_write);
dce(c, inst);
progress = true;
continue;