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aco: Workarounds subdword lowering on GFX6/7 

As there are no SDWA instructions, we need to take care not to overwrite
the upper bits of other copy_operation's operands.

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5226>
This commit is contained in:
Daniel Schürmann 2020-05-16 17:30:21 +01:00 committed by Marge Bot
parent 942e3c40c3
commit b083581010
1 changed files with 43 additions and 0 deletions
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43
src/amd/compiler/aco_lower_to_hw_instr.cpp
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@ -1165,6 +1165,9 @@ void do_swap(lower_context *ctx, Builder& bld, const copy_operation& copy, bool
offset += def.bytes();
}
if (ctx->program->chip_class <= GFX7)
return;
/* fixup in case we swapped bytes we shouldn't have */
copy_operation tmp_copy = copy;
tmp_copy.op.setFixed(copy.def.physReg());
@ -1250,6 +1253,46 @@ void handle_operands(std::map<PhysReg, copy_operation>& copy_map, lower_context*
}
// TODO: try to coalesce subdword copies
/* on GFX6/7, we need some small workarounds as there is no
* SDWA instruction to do partial register writes */
if (ctx->program->chip_class < GFX8 && it->second.bytes == 2) {
if (it->first.byte() == 0 && it->second.op.physReg().byte() == 0 &&
!it->second.is_used && pi->opcode == aco_opcode::p_split_vector) {
/* Other operations might overwrite the high bits, so change all users
* of the high bits to the new target where they are still available.
* This mechanism depends on also emitting dead definitions. */
PhysReg reg_hi = it->second.op.physReg().advance(2);
std::map<PhysReg, copy_operation>::iterator other = copy_map.begin();
for (other = copy_map.begin(); other != copy_map.end(); other++) {
/* on GFX6/7, if the high bits are used as operand, they cannot be a target */
if (other->second.op.physReg() == reg_hi) {
other->second.op.setFixed(it->first.advance(2));
break; /* break because an operand can only be used once */
}
}
} else if (it->first.byte() == 2) {
/* on GFX6/7, if we target an upper half where the lower half hasn't yet been handled,
* move to the target operand's high bits. This is save to do as it cannot be an operand */
PhysReg lo = PhysReg(it->first.reg());
std::map<PhysReg, copy_operation>::iterator other = copy_map.find(lo);
if (other != copy_map.end()) {
PhysReg new_reg_hi = other->second.op.physReg().advance(2);
assert(other->second.bytes == 2 && new_reg_hi.byte() == 2);
it->second.def = Definition(new_reg_hi, v2b);
it->second.is_used = 0;
other->second.bytes = 4;
other->second.def.setTemp(Temp(other->second.def.tempId(), v1));
other->second.op.setTemp(Temp(other->second.op.tempId(), v1));
/* if the new target's high bits are also a target, change uses */
std::map<PhysReg, copy_operation>::iterator target = copy_map.find(new_reg_hi);
if (target != copy_map.end()) {
target->second.uses[0]++;
target->second.uses[1]++;
}
}
}
}
/* find portions where the target reg is not used as operand for any other copy */
if (it->second.is_used) {
if (it->second.op.isConstant()) {