From 87bfed33e90831d1aa6fd9fa0e66fb7acf5a8da6 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Daniel=20Sch=C3=BCrmann?= Date: Fri, 11 Dec 2020 19:37:50 +0100 Subject: [PATCH] aco/spill: only prevent rematerializable vars from being DCE'd if they haven't been renamed The small DCE of the spiller only removes the original instructions of rematerialized variables in case they are unused. If a variable has been renamed, it cannot match any original instruction anymore. Thus, the lookup is then unnecessary and can be omitted. No fossil-db changes. Reviewed-by: Rhys Perry Part-of: (cherry picked from commit ef4101d6d73614f4f41708050f963d6038f91e25) --- .pick_status.json | 2 +- src/amd/compiler/aco_spill.cpp | 37 +++++++++++++++------------------- 2 files changed, 17 insertions(+), 22 deletions(-) diff --git a/.pick_status.json b/.pick_status.json index fba15fa2500..483ba866d0d 100644 --- a/.pick_status.json +++ b/.pick_status.json @@ -706,7 +706,7 @@ "description": "aco/spill: only prevent rematerializable vars from being DCE'd if they haven't been renamed", "nominated": false, "nomination_type": null, - "resolution": 4, + "resolution": 1, "master_sha": null, "because_sha": null }, diff --git a/src/amd/compiler/aco_spill.cpp b/src/amd/compiler/aco_spill.cpp index e114e2e1abc..fbb5a29a24f 100644 --- a/src/amd/compiler/aco_spill.cpp +++ b/src/amd/compiler/aco_spill.cpp @@ -814,12 +814,6 @@ void add_coupling_code(spill_ctx& ctx, Block* block, unsigned block_idx) phi->opcode != aco_opcode::p_linear_phi) break; - /* prevent it's definining instruction from being DCE'd if it could be rematerialized */ - for (const Operand& op : phi->operands) { - if (op.isTemp() && ctx.remat.count(op.getTemp())) - ctx.remat_used[ctx.remat[op.getTemp()].instr] = true; - } - /* if the phi is not spilled, add to instructions */ if (ctx.spills_entry[block_idx].find(phi->definitions[0].getTemp()) == ctx.spills_entry[block_idx].end()) { instructions.emplace_back(std::move(phi)); @@ -837,6 +831,11 @@ void add_coupling_code(spill_ctx& ctx, Block* block, unsigned block_idx) assert(phi->operands[i].isTemp() && phi->operands[i].isKill()); Temp var = phi->operands[i].getTemp(); + std::map::iterator rename_it = ctx.renames[pred_idx].find(var); + /* prevent the definining instruction from being DCE'd if it could be rematerialized */ + if (rename_it == ctx.renames[preds[i]].end() && ctx.remat.count(var)) + ctx.remat_used[ctx.remat[var].instr] = true; + /* build interferences between the phi def and all spilled variables at the predecessor blocks */ for (std::pair pair : ctx.spills_exit[pred_idx]) { if (var == pair.first) @@ -853,7 +852,6 @@ void add_coupling_code(spill_ctx& ctx, Block* block, unsigned block_idx) } /* rename if necessary */ - std::map::iterator rename_it = ctx.renames[pred_idx].find(var); if (rename_it != ctx.renames[pred_idx].end()) { var = rename_it->second; ctx.renames[pred_idx].erase(rename_it); @@ -944,6 +942,9 @@ void add_coupling_code(spill_ctx& ctx, Block* block, unsigned block_idx) std::map::iterator it = ctx.renames[pred_idx].find(phi->operands[i].getTemp()); if (it != ctx.renames[pred_idx].end()) phi->operands[i].setTemp(it->second); + /* prevent the definining instruction from being DCE'd if it could be rematerialized */ + else if (ctx.remat.count(phi->operands[i].getTemp())) + ctx.remat_used[ctx.remat[phi->operands[i].getTemp()].instr] = true; continue; } @@ -1033,12 +1034,16 @@ void add_coupling_code(spill_ctx& ctx, Block* block, unsigned block_idx) rename = {ctx.program->allocateId(), pair.first.regClass()}; for (unsigned i = 0; i < phi->operands.size(); i++) { Temp tmp; - if (ctx.renames[preds[i]].find(pair.first) != ctx.renames[preds[i]].end()) + if (ctx.renames[preds[i]].find(pair.first) != ctx.renames[preds[i]].end()) { tmp = ctx.renames[preds[i]][pair.first]; - else if (preds[i] >= block_idx) + } else if (preds[i] >= block_idx) { tmp = rename; - else + } else { tmp = pair.first; + /* prevent the definining instruction from being DCE'd if it could be rematerialized */ + if (ctx.remat.count(tmp)) + ctx.remat_used[ctx.remat[tmp].instr] = true; + } phi->operands[i] = Operand(tmp); } phi->definitions[0] = Definition(rename); @@ -1101,7 +1106,7 @@ void process_block(spill_ctx& ctx, unsigned block_idx, Block* block, if (ctx.renames[block_idx].find(op.getTemp()) != ctx.renames[block_idx].end()) op.setTemp(ctx.renames[block_idx][op.getTemp()]); /* prevent it's definining instruction from being DCE'd if it could be rematerialized */ - if (ctx.remat.count(op.getTemp())) + else if (ctx.remat.count(op.getTemp())) ctx.remat_used[ctx.remat[op.getTemp()].instr] = true; continue; } @@ -1245,16 +1250,6 @@ void spill_block(spill_ctx& ctx, unsigned block_idx) /* add coupling code to all loop header predecessors */ add_coupling_code(ctx, loop_header, loop_header->index); - /* update remat_used for phis added in add_coupling_code() */ - for (aco_ptr& instr : loop_header->instructions) { - if (!is_phi(instr)) - break; - for (const Operand& op : instr->operands) { - if (op.isTemp() && ctx.remat.count(op.getTemp())) - ctx.remat_used[ctx.remat[op.getTemp()].instr] = true; - } - } - /* propagate new renames through loop: i.e. repair the SSA */ renames.swap(ctx.renames[loop_header->index]); for (std::pair rename : renames) {