VarAction2: Infer ternary add result is bool if both branches are bool

src/newgrf_optimiser.cpp

@@ -350,21 +350,9 @@ static VarAction2AdjustsBooleanInverseResult AreVarAction2AdjustsBooleanInverse(
 	return VA2ABIR_NO;
 }
 
-/*
+static void GetBoolMulSourceAdjusts(std::vector<DeterministicSpriteGroupAdjust> &adjusts, int start_index, uint store_var, DeterministicSpriteGroupAdjust &synth_adjust,
- * Find and replace the result of:
+	VarAction2AdjustDescriptor &found1, VarAction2AdjustDescriptor &found2, uint *mul_index)
- *   (var * flag) + (var * !flag) with var
- *   (-var * (var < 0)) + (var * !(var < 0)) with abs(var)
- * "+" may be ADD, OR or XOR.
- */
-static bool TryMergeBoolMulCombineVarAction2Adjust(VarAction2OptimiseState &state, std::vector<DeterministicSpriteGroupAdjust> &adjusts, const int adjust_index)
 {
-	uint store_var = adjusts[adjust_index].parameter;
-
-	DeterministicSpriteGroupAdjust synth_adjusts[2];
-	VarAction2AdjustDescriptor found_adjusts[4] = {};
-	uint mul_indices[2] = {};
-
-	auto find_adjusts = [&](int start_index, uint save_index) {
 	bool have_mul = false;
 	for (int i = start_index; i >= 0; i--) {
 		const DeterministicSpriteGroupAdjust &prev = adjusts[i];
@@ -382,21 +370,21 @@ static bool TryMergeBoolMulCombineVarAction2Adjust(VarAction2OptimiseState &stat
 			}
 		} else if (prev.operation == DSGA_OP_MUL && !have_mul) {
 			/* First source is the variable of mul, if it's a temporary storage load, try to follow it */
-				mul_indices[save_index] = i;
+			if (mul_index != nullptr) *mul_index = i;
 			if (prev.variable == 0x7D && prev.type == DSGA_TYPE_NONE && prev.shift_num == 0 && prev.and_mask == 0xFFFFFFFF) {
 				int store_index = GetVarAction2AdjustOfPreviousTempStoreSource(adjusts.data(), i - 1, (prev.parameter & 0xFF));
 				if (store_index >= 1) {
 					/* Found the referenced temp store, use that */
-						found_adjusts[save_index * 2] = { adjusts.data(), nullptr, store_index - 1 };
+					found1 = { adjusts.data(), nullptr, store_index - 1 };
 					have_mul = true;
 				}
 			}
 			if (!have_mul) {
 				/* It's not a temporary storage load which can be followed, synthesise an RST */
-					synth_adjusts[save_index] = prev;
+				synth_adjust = prev;
-					synth_adjusts[save_index].operation = DSGA_OP_RST;
+				synth_adjust.operation = DSGA_OP_RST;
-					synth_adjusts[save_index].adjust_flags = DSGAF_NONE;
+				synth_adjust.adjust_flags = DSGAF_NONE;
-					found_adjusts[save_index * 2] = { adjusts.data(), synth_adjusts + save_index, i };
+				found1 = { adjusts.data(), &synth_adjust, i };
 				have_mul = true;
 			}
 		} else if (prev.operation == DSGA_OP_STOP) {
@@ -404,12 +392,30 @@ static bool TryMergeBoolMulCombineVarAction2Adjust(VarAction2OptimiseState &stat
 			return;
 		} else if (have_mul) {
 			/* Found second source */
-				found_adjusts[(save_index * 2) + 1] = { adjusts.data(), nullptr, i };
+			found2 = { adjusts.data(), nullptr, i };
 			return;
 		} else {
 			return;
 		}
 	}
+}
+
+/*
+ * Find and replace the result of:
+ *   (var * flag) + (var * !flag) with var
+ *   (-var * (var < 0)) + (var * !(var < 0)) with abs(var)
+ * "+" may be ADD, OR or XOR.
+ */
+static bool TryMergeBoolMulCombineVarAction2Adjust(VarAction2OptimiseState &state, std::vector<DeterministicSpriteGroupAdjust> &adjusts, const int adjust_index)
+{
+	uint store_var = adjusts[adjust_index].parameter;
+
+	DeterministicSpriteGroupAdjust synth_adjusts[2];
+	VarAction2AdjustDescriptor found_adjusts[4] = {};
+	uint mul_indices[2] = {};
+
+	auto find_adjusts = [&](int start_index, uint save_index) {
+		GetBoolMulSourceAdjusts(adjusts, start_index, store_var, synth_adjusts[save_index], found_adjusts[save_index * 2], found_adjusts[(save_index * 2) + 1], mul_indices + save_index);
 	};
 
 	find_adjusts(adjust_index - 1, 0); // A (first, closest)
@@ -1051,6 +1057,41 @@ void OptimiseVarAction2Adjust(VarAction2OptimiseState &state, const GrfSpecFeatu
 			}
 			switch (adjust.operation) {
 				case DSGA_OP_ADD:
+					if (adjust.variable == 0x7D && adjust.shift_num == 0 && adjust.and_mask == 0xFFFFFFFF &&
+							(prev_inference & VA2AIF_ONE_OR_ZERO) && (non_const_var_inference & VA2AIF_ONE_OR_ZERO) &&
+							((prev_inference & VA2AIF_MUL_BOOL) || (non_const_var_inference & VA2AIF_MUL_BOOL))) {
+						/* See if this is a ternary operation where both cases result in bool */
+						auto check_ternary_bool = [&]() -> bool {
+							int store_index = GetVarAction2AdjustOfPreviousTempStoreSource(group->adjusts.data(), ((int)group->adjusts.size()) - 2, (adjust.parameter & 0xFF));
+							if (store_index < 0) return false;
+
+							DeterministicSpriteGroupAdjust synth_adjusts[2];
+							VarAction2AdjustDescriptor found_adjusts[4] = {};
+
+							if (prev_inference & VA2AIF_MUL_BOOL) {
+								GetBoolMulSourceAdjusts(group->adjusts, ((int)group->adjusts.size()) - 2, adjust.parameter, synth_adjusts[0], found_adjusts[0], found_adjusts[1], nullptr);
+							} else if (group->adjusts.size() >= 2) {
+								found_adjusts[0] = { group->adjusts.data(), nullptr, ((int)group->adjusts.size()) - 2 };
+							}
+							if (!found_adjusts[0].IsValid() && !found_adjusts[1].IsValid()) return false;
+
+							if (non_const_var_inference & VA2AIF_MUL_BOOL) {
+								GetBoolMulSourceAdjusts(group->adjusts, store_index - 1, adjust.parameter, synth_adjusts[1], found_adjusts[2], found_adjusts[3], nullptr);
+							} else if (store_index >= 1) {
+								found_adjusts[2] = { group->adjusts.data(), nullptr, store_index - 1 };
+							}
+							if (!found_adjusts[2].IsValid() && !found_adjusts[3].IsValid()) return false;
+
+							if (AreVarAction2AdjustsBooleanInverse(found_adjusts[0], found_adjusts[2]) != VA2ABIR_NO) return true;
+							if (AreVarAction2AdjustsBooleanInverse(found_adjusts[0], found_adjusts[3]) != VA2ABIR_NO) return true;
+							if (AreVarAction2AdjustsBooleanInverse(found_adjusts[1], found_adjusts[2]) != VA2ABIR_NO) return true;
+							if (AreVarAction2AdjustsBooleanInverse(found_adjusts[1], found_adjusts[3]) != VA2ABIR_NO) return true;
+							return false;
+						};
+						if (check_ternary_bool()) {
+							state.inference |= VA2AIF_ONE_OR_ZERO | VA2AIF_SIGNED_NON_NEGATIVE;
+						}
+					}
 					try_merge_with_previous();
 					break;
 				case DSGA_OP_SUB: