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aco/spill: only prevent rematerializable vars from being DCE'd if they haven't been renamed

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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 <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8055>
(cherry picked from commit ef4101d6d7)
This commit is contained in:
Daniel Schürmann 2020-12-11 19:37:50 +01:00 • committed by Dylan Baker
parent 17ea1b0540
commit 87bfed33e9
2 changed files with 17 additions and 22 deletions
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2
.pick_status.json
View file

@ -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
},

37
src/amd/compiler/aco_spill.cpp
View file

@ -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<Temp, Temp>::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<Temp, uint32_t> 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<Temp, Temp>::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<Temp, Temp>::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<Instruction>& 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<Temp, Temp> rename : renames) {