72 lines
1.7 KiB
C++
72 lines
1.7 KiB
C++
/*
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Copyright (c) 2016 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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*/
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#include "library/vm/vm.h"
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namespace lean {
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static void del_instr_at(unsigned pc, buffer<vm_instr> & code) {
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code.erase(pc);
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// we must adjust pc of other instructions
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for (unsigned i = 0; i < code.size(); i++) {
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vm_instr & c = code[i];
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for (unsigned j = 0; j < c.get_num_pcs(); j++) {
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if (c.get_pc(j) > pc)
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c.set_pc(j, c.get_pc(j) - 1);
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}
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}
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}
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/**
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\brief Applies the following transformation
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...
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pc: drop n
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pc+1: drop m
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...
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===>
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...
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pc: drop n+m
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... */
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static void compress_drop_drop(buffer<vm_instr> & code) {
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if (code.empty()) return;
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unsigned i = code.size() - 1;
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while (i > 0) {
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--i;
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if (code[i].op() == opcode::Drop &&
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code[i+1].op() == opcode::Drop) {
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code[i] = mk_drop_instr(code[i].get_num() + code[i+1].get_num());
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del_instr_at(i+1, code);
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}
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}
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}
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/**
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\brief Applies the following transformation
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pc_1 : goto pc_2
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...
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pc_2 : ret
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===>
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pc_1 : ret
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...
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pc_2 : ret */
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static void compress_goto_ret(buffer<vm_instr> & code) {
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unsigned i = code.size();
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while (i > 0) {
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--i;
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if (code[i].op() == opcode::Goto) {
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unsigned pc = code[i].get_goto_pc();
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if (code[pc].op() == opcode::Ret) {
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code[i] = mk_ret_instr();
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}
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}
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}
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}
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void optimize(environment const &, buffer<vm_instr> & code) {
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compress_goto_ret(code);
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compress_drop_drop(code);
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}
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}
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