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aco/lower_branches: properly consider exec mask needs of branch targets

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Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33619>
This commit is contained in:
Daniel Schürmann 2025-03-06 14:05:35 +01:00 • committed by Marge Bot
parent c37ece75ea
commit c1b124ab6c
2 changed files with 12 additions and 12 deletions
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3
src/amd/compiler/aco_ir.cpp
View file

@ -855,7 +855,8 @@ needs_exec_mask(const Instruction* instr)
if (instr->isSALU() || instr->isBranch() || instr->isSMEM() || instr->isBarrier())
return instr->opcode == aco_opcode::s_cbranch_execz ||
instr->opcode == aco_opcode::s_cbranch_execnz || instr->reads_exec();
instr->opcode == aco_opcode::s_cbranch_execnz ||
instr->opcode == aco_opcode::s_setpc_b64 || instr->reads_exec();
if (instr->isPseudo()) {
switch (instr->opcode) {

21
src/amd/compiler/aco_lower_branches.cpp
View file

@ -272,26 +272,25 @@ try_merge_break_with_continue(branch_ctx& ctx, Block& block)
void
eliminate_useless_exec_writes_in_block(branch_ctx& ctx, Block& block)
{
/* Check if any successor needs the outgoing exec mask from the current block. */
bool exec_write_used;
bool exec_write_used = false;
if (block.kind & block_kind_end_with_regs) {
/* Last block of a program with succeed shader part should respect final exec write. */
exec_write_used = true;
} else if (block.linear_succs.empty() && !block.instructions.empty() &&
block.instructions.back()->opcode == aco_opcode::s_setpc_b64) {
/* This block ends in a long jump and exec might be needed for the next shader part. */
exec_write_used = true;
} else {
/* blocks_incoming_exec_used is initialized to true, so this is correct even for loops. */
exec_write_used =
std::any_of(block.linear_succs.begin(), block.linear_succs.end(),
[&ctx](int succ_idx) { return ctx.blocks_incoming_exec_used[succ_idx]; });
} else if (!block.linear_succs.empty()) {
/* Check if the successor needs the outgoing exec mask from the current block. */
exec_write_used = ctx.blocks_incoming_exec_used[block.linear_succs[0]];
}
/* Go through all instructions and eliminate useless exec writes. */
for (int i = block.instructions.size() - 1; i >= 0; --i) {
aco_ptr<Instruction>& instr = block.instructions[i];
/* blocks_incoming_exec_used is initialized to true, so this is correct even for loops. */
if (instr->opcode == aco_opcode::s_cbranch_scc0 ||
instr->opcode == aco_opcode::s_cbranch_scc1) {
exec_write_used |= ctx.blocks_incoming_exec_used[instr->salu().imm];
}
/* See if the current instruction needs or writes exec. */
bool needs_exec = needs_exec_mask(instr.get());
bool writes_exec =