From b36757448dd79a062347c377d4f65b94bfcfaad3 Mon Sep 17 00:00:00 2001 From: Eric Anholt Date: Sat, 29 Dec 2018 12:44:22 -0800 Subject: [PATCH] v3d: Dead-code eliminate unused flags updates. 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%) --- src/broadcom/compiler/vir_opt_dead_code.c | 46 +++++++++++++++++++++-- 1 file changed, 42 insertions(+), 4 deletions(-) diff --git a/src/broadcom/compiler/vir_opt_dead_code.c b/src/broadcom/compiler/vir_opt_dead_code.c index 9c93846e9b8..a486708bfa5 100644 --- a/src/broadcom/compiler/vir_opt_dead_code.c +++ b/src/broadcom/compiler/vir_opt_dead_code.c @@ -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; -- 2.30.2