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VarAction2: If DSE results in a redundant load, remove it

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This commit is contained in:
Jonathan G Rennison
2022-06-07 19:25:08 +01:00
parent 86324e0fda
commit a8c0e47dd8
1 changed files with 37 additions and 20 deletions
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57
src/newgrf.cpp
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@@ -5705,6 +5705,34 @@ static bool IsFeatureUsableForDSE(GrfSpecFeature feature)
return (feature != GSF_STATIONS);
}
static const DeterministicSpriteGroupAdjust *GetVarAction2PreviousSingleLoadAdjust(const std::vector<DeterministicSpriteGroupAdjust> &adjusts, int start_index)
{
for (int i = start_index; i >= 0; i--) {
const DeterministicSpriteGroupAdjust &prev = adjusts[i];
if (prev.variable == 0x7E) {
/* Procedure call, don't use or go past this */
break;
}
if (prev.operation == DSGA_OP_RST) {
return &prev;
} else if (prev.operation == DSGA_OP_STO) {
if (prev.type == DSGA_TYPE_NONE && prev.variable == 0x1A && prev.shift_num == 0 && prev.and_mask < 0x100) {
/* Temp store */
continue;
} else {
/* Special register store or unpredictable store, don't try to optimise following load */
break;
}
} else if (prev.operation == DSGA_OP_STOP) {
/* Permanent storage store */
continue;
} else {
break;
}
}
return nullptr;
}
static void OptimiseVarAction2Adjust(VarAction2OptimiseState &state, const GrfSpecFeature feature, const byte varsize, DeterministicSpriteGroup *group, DeterministicSpriteGroupAdjust &adjust)
{
if (unlikely(HasGrfOptimiserFlag(NGOF_NO_OPT_VARACT2))) return;
@@ -5826,26 +5854,7 @@ static void OptimiseVarAction2Adjust(VarAction2OptimiseState &state, const GrfSp
if (feature == GSF_INDUSTRYTILES && group->var_scope == VSG_SCOPE_SELF && IsExpensiveIndustryTileVariable(adjust.variable)) state.check_expensive_vars = true;
auto get_prev_single_load = [&]() -> const DeterministicSpriteGroupAdjust* {
for (int i = (int)group->adjusts.size() - 2; i >= 0; i--) {
const DeterministicSpriteGroupAdjust &prev = group->adjusts[i];
if (prev.operation == DSGA_OP_RST) {
return &prev;
} else if (prev.operation == DSGA_OP_STO) {
if (prev.type == DSGA_TYPE_NONE && prev.variable == 0x1A && prev.shift_num == 0 && prev.and_mask < 0x100) {
/* Temp store */
continue;
} else {
/* Special register store or unpredictable store, don't try to optimise following load */
break;
}
} else if (prev.operation == DSGA_OP_STOP) {
/* Permanent storage store */
continue;
} else {
break;
}
}
return nullptr;
return GetVarAction2PreviousSingleLoadAdjust(group->adjusts, (int)group->adjusts.size() - 2);
};
if ((prev_inference & VA2AIF_SINGLE_LOAD) && adjust.operation == DSGA_OP_RST && adjust.variable != 0x1A && adjust.variable != 0x7D && adjust.variable != 0x7E) {
@@ -6745,6 +6754,14 @@ static void HandleVarAction2DeadStoreElimination(DeterministicSpriteGroup *group
restart();
break;
}
if (next.operation == DSGA_OP_RST) {
/* See if this is a repeated load of a variable (not procedure call) */
const DeterministicSpriteGroupAdjust *prev_load = GetVarAction2PreviousSingleLoadAdjust(group->adjusts, i);
if (prev_load != nullptr && MemCmpT<DeterministicSpriteGroupAdjust>(prev_load, &next) == 0) {
group->adjusts.erase(group->adjusts.begin() + i + 1);
break;
}
}
}
break;
}