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// Copyright 2015 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/// Forward loads/stores through RSP relative slots.
/// Assumes stack operations are well-behaved and all stack operations are
/// implicit in the IR.
library saga.flow.locals;
import 'package:saga/src/flow/node.dart';
import 'package:saga/src/flow/cpu_register.dart';
import 'package:saga/src/flow/ssa.dart';
import 'package:saga/src/util.dart';
findLocals(state, blocks) {
final entrySp = state.entryState[CpuRegister.RSP];
final offsets = new Map<Node, int>();
rewire(def, int offset) {
for (Use use in iterate(def.uses)) {
final node = use.at;
if (node.op == ADD || (node.op == SUB && use.idx == 0)) {
final otherVal = node.inputs[1 - use.idx].def;
if (otherVal.op is OpKonstant) {
final int offs = otherVal.op.value;
final int new_offset = offset + (node.op == SUB ? -offs : offs);
if (def != entrySp) {
final new_addr = Node.binary(ADD, entrySp, Node.konst(new_offset));
node.replaceWith(new_addr);
rewire(new_addr, new_offset);
} else {
rewire(node, new_offset);
}
continue;
}
} else if (node.op is OpAddr) {
assert(use.idx == 0);
assert(node.inputs[1].def == null);
if (def != entrySp) {
final new_addr = Node.addr(
base: entrySp,
offset: node.op.offset + offset);
node.replaceWith(new_addr);
rewire(new_addr, new_addr.op.offset);
} else {
rewire(node, node.op.offset);
}
continue;
} else if (node.op == LOAD || node.op == STORE) {
offsets[node] = offset;
continue;
} else if (node.op == PHANTOM) {
continue; // ignore phantoms
}
throw "can't establish the flow of RSP: ${def.opcode}";
}
}
rewire(entrySp, 0);
final ssa = new SSABuilder(blocks);
for (var block in blocks) {
ssa.startBlock(block);
for (var node in iterate(block.code)) {
final offset = offsets[node];
if (offset != null) {
if (node.op == STORE) {
ssa.define(offset, node.inputs[1].def);
} else {
node.replaceUses(ssa.use(offset));
node.remove();
}
}
}
}
ssa.finish();
}