projects/08/src/codewriter.h
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#ifndef _CODEWRITER_H #define _CODEWRITER_H // 'codewriter.h' roughly corresponds to the 'CodeWriter' module specified in // nand2tetris, with a few liberties taken. #include <stdbool.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include "parser.h" #include "util.h" #define _DEBUG // memory mapping: // 0-15 virtual registers R0-R15 // 16-255 static variables // 256-2047 stack #define SP (0) // points to word ahead of top of stack #define LCL (1) // points to local segment #define ARG (2) // points to argument segment #define POINTER (3) #define THIS (3) #define THAT (4) #define TEMP (5) #define R13 (13) // R13-R15 are scratch space that #define R14 (14) // VM-generated assembly can use #define R15 (15) // for whatever. #define STATIC (16) // start of static variables segment (240 words, 16-255) char *static_sym_name; // static segment index indexes into map, retrieves hack assembly symbol offset #define MAX_STATIC_SYMBOLS (240) // for whatever. uint16_t static_symbol_map[MAX_STATIC_SYMBOLS]; uint8_t g_symbol_offset_bump = 0; // holds current largest symbol offset, bumps char comp_vm_funcs[] = "@__comp_funcs_end\n" "0;JMP\n" "\n" "(__test_eq)\n" "@SP\n" "AM=M-1\n" // RAM[SP]--, A = RAM[SP] "D=M\n" // D = RAM[SP] (top stack val) "A=A-1\n" // --A (--> bottom stack val) "D=M-D\n" // if D == 0, equal "M=0\n" // prematurely push false "@__test_eq_neq\n" // if D == 0, equal "D;JNE\n" // if D != 0, not equal, jump "@SP\n" // get SP "A=M-1\n" // get bottom stack val address "M=-1\n" // push 0xffff (true) "(__test_eq_neq)\n" "@R13\n" // return address in RAM[R13] "A=M\n" // A = return address "0;JMP\n" // return "\n" "(__test_gt)\n" "@SP\n" "AM=M-1\n" // RAM[SP]--, A = RAM[SP] "D=M\n" // D = RAM[SP] (top stack val) "A=A-1\n" // --A (--> bottom stack val) "D=M-D\n" // if (D - M) > 0; push true "M=0\n" // prematurely push false "@__test_gt_neq\n" // if D == 0, equal "D;JLE\n" // if D != 0, not equal, jump "@SP\n" // get SP "A=M-1\n" // get bottom stack val address "M=-1\n" // push 0xffff (true) "(__test_gt_neq)\n" "@R13\n" // return address in RAM[R13] "A=M\n" // A = return address "0;JMP\n" // return "\n" "(__test_lt)\n" "@SP\n" "AM=M-1\n" // RAM[SP]--, A = RAM[SP] "D=M\n" // D = RAM[SP] (top stack val) "A=A-1\n" // --A (--> bottom stack val) "D=M-D\n" // if (D - M) < 0; push true "M=0\n" // prematurely push false "@__test_lt_neq\n" // if D == 0, equal "D;JGE\n" // if D != 0, not equal, jump "@SP\n" // get SP "A=M-1\n" // get bottom stack val address "M=-1\n" // push 0xffff (true) "(__test_lt_neq)\n" "@R13\n" // return address in RAM[R13] "A=M\n" // A = return address "0;JMP\n" // return "\n" "(__comp_funcs_end)\n"; char vm_init[] = "@256\n" // start address of stack (nothing pushed yet) "D=A\n" // D = 256 "@SP\n" // A = <constant representing address of SP> "M=D\n" // <memory pointed to by SP> = 256 "@Sys.init\n" // jump to Sys.init function (not call since "0;JMP\n\n"; // we don't need to set up the stack) // TODO: add initializers for argument, local, static, constant, this, that // TODO only output vm_stop when Main.main char vm_stop[] = "(END)\n" // starting address of stack (nothing pushed yet) "@END\n" // D = 256 "0;JMP\n"; // A = <constant representing address of SP> void write_vm_init(FILE *fp) { fprintf(fp, "%s", vm_init); // can (un)comment to toggle init behavior fprintf(fp, "%s\n", comp_vm_funcs); } void write_vm_stop(FILE *fp) { fprintf(fp, "\n%s", vm_stop); } static bool write_arithmetic(struct vm_instruction_t *vm_instr, FILE *fp) { char binary_op_template[] = "@SP\n" "AM=M-1\n" // RAM[SP]--, A = RAM[SP] "D=M\n" // D = RAM[SP] (top stack val) "A=A-1\n" // --A (--> bottom stack val) "%s"; // arithmetic op goes here char unary_op_template[] = "@SP\n" "A=M-1\n" // A = SP - 1 "%s"; // arithmetic op goes here char op_add[] = "M=D+M\n"; char op_sub[] = "M=M-D\n"; char op_eq[] = "@%s_%lu_eq\n" // <- static_sym_name, file_line_number "D=A\n" "@R13\n" "M=D\n" "@__test_eq\n" "0;JMP\n" "(%s_%lu_eq)\n" // return here "\n"; char op_gt[] = "@%s_%lu_gt\n" // <- static_sym_name, file_line_number "D=A\n" "@R13\n" "M=D\n" "@__test_gt\n" "0;JMP\n" "(%s_%lu_gt)\n" // return here "\n"; char op_lt[] = "@%s_%lu_lt\n" // <- static_sym_name, file_line_number "D=A\n" "@R13\n" "M=D\n" "@__test_lt\n" "0;JMP\n" "(%s_%lu_lt)\n" // return here "\n"; char op_and[] = "M=D&M\n"; char op_or[] = "M=D|M\n"; char op_neg[] = "M=-M\n"; char op_not[] = "M=!M\n"; // binary operations if (!strncmp(vm_instr->arg1, "add", CMD_STR_MAX_LEN)) { fprintf(fp, binary_op_template, op_add); } else if (!strncmp(vm_instr->arg1, "sub", CMD_STR_MAX_LEN)) { fprintf(fp, binary_op_template, op_sub); } else if (!strncmp(vm_instr->arg1, "eq", CMD_STR_MAX_LEN)) { fprintf(fp, op_eq, static_sym_name, file_line_no, static_sym_name, file_line_no); } else if (!strncmp(vm_instr->arg1, "gt", CMD_STR_MAX_LEN)) { fprintf(fp, op_gt, static_sym_name, file_line_no, static_sym_name, file_line_no); } else if (!strncmp(vm_instr->arg1, "lt", CMD_STR_MAX_LEN)) { fprintf(fp, op_lt, static_sym_name, file_line_no, static_sym_name, file_line_no); } else if (!strncmp(vm_instr->arg1, "and", CMD_STR_MAX_LEN)) { fprintf(fp, binary_op_template, op_and); } else if (!strncmp(vm_instr->arg1, "or", CMD_STR_MAX_LEN)) { fprintf(fp, binary_op_template, op_or); // unary operations } else if (!strncmp(vm_instr->arg1, "neg", CMD_STR_MAX_LEN)) { fprintf(fp, unary_op_template, op_neg); } else if (!strncmp(vm_instr->arg1, "not", CMD_STR_MAX_LEN)) { fprintf(fp, unary_op_template, op_not); } else { err("error: invalid arithmetic op \"%s\"\n", vm_instr->arg1); return false; } return true; } static bool resolve_static_address(struct vm_instruction_t *vm_instr, uint16_t *addr) { uint16_t symbol_offset; if (vm_instr->arg2 >= MAX_STATIC_SYMBOLS) { err("error: arg2 too large, >= %u\n", MAX_STATIC_SYMBOLS); return false; } symbol_offset = static_symbol_map[vm_instr->arg2]; if (symbol_offset == 0xffff) { // new offset not in map (-1 special) if (g_symbol_offset_bump >= MAX_STATIC_SYMBOLS) { err("error: symbol offset grew too large (>= %u), " "too many static variables\n", MAX_STATIC_SYMBOLS); return false; } static_symbol_map[vm_instr->arg2] = g_symbol_offset_bump; *addr = g_symbol_offset_bump; ++g_symbol_offset_bump; // bump global symbol offset } else { // offset found in map, return symbol value/index *addr = symbol_offset; } return true; } // push 16-bit value from segment offset onto top of stack static bool write_push(struct vm_instruction_t *vm_instr, FILE *fp) { uint16_t addr, arg2 = vm_instr->arg2; // TODO: could add SP counter/check to catch overflows char const_template[] = "@%hu\n" // A = constant "D=A\n%s"; // D = constant char addr_template[] = "@%hu\n" // A = segment + index "D=M\n%s"; // D = RAM[segment + index] char static_template[] = "@%s.%hu\n" // A = segment + index "D=M\n%s"; // D = RAM[segment + index] char indirect_template[] = "@%hu\n" // A = segment "D=M\n" // D = RAM[segment] "@%hu\n" // A = index "A=A+D\n" // A = segment + index "D=M\n%s"; // D = RAM[segment + index] char push_boilerplate[] = "@SP\n" "M=M+1\n" // RAM[SP]++ // inc SP "A=M-1\n" // A = RAM[SP] - 1 // prev top "M=D\n"; // RAM[SP] = constant if (!strcmp(vm_instr->arg1, "constant")) { // TODO: check size of constant (allowed to be > 32,767?) // TODO: look in nand2tetris forums in case issue already noted fprintf(fp, const_template, arg2, push_boilerplate); } else if (!strcmp(vm_instr->arg1, "argument")) { fprintf(fp, indirect_template, ARG, arg2, push_boilerplate); } else if (!strcmp(vm_instr->arg1, "local")) { fprintf(fp, indirect_template, LCL, arg2, push_boilerplate); } else if (!strcmp(vm_instr->arg1, "static")) { if (!resolve_static_address(vm_instr, &addr)) { return false; } fprintf(fp, static_template, static_sym_name, addr, push_boilerplate); } else if (!strcmp(vm_instr->arg1, "this")) { fprintf(fp, indirect_template, THIS, arg2, push_boilerplate); } else if (!strcmp(vm_instr->arg1, "that")) { fprintf(fp, indirect_template, THAT, arg2, push_boilerplate); } else if (!strcmp(vm_instr->arg1, "pointer")) { addr = POINTER + vm_instr->arg2; fprintf(fp, addr_template, addr, push_boilerplate); } else if (!strcmp(vm_instr->arg1, "temp")) { addr = TEMP + vm_instr->arg2; fprintf(fp, addr_template, addr, push_boilerplate); } else { err("error: invalid segment name \"%s\"\n", vm_instr->arg1); return false; } return true; } // pop 16-bit value from top of stack into segment offset static bool write_pop(struct vm_instruction_t *vm_instr, FILE *fp) { // TODO: could add SP counter/check to catch overflows uint16_t addr, arg2 = vm_instr->arg2; char pop_indirect_template[] = "@%hu\n" // @segment "D=M\n" // D = segment "@%hu\n" // @index "D=A+D\n" // A = segment + index "@R13\n" "M=D\n" // RAM[13] = segment + index "@SP\n" // "AM=M-1\n" // "D=M\n" // "@R13\n" // "A=M\n" // "M=D\n"; // char pop_addr_template[] = "@SP\n" "AM=M-1\n" // decrement SP "D=M\n" // "pop" (read) value into D "@%hu\n" // load address "M=D\n"; // "pop" (write) value to RAM char pop_static_template[] = "@SP\n" "AM=M-1\n" // decrement SP "D=M\n" // "pop" (read) value into D "@%s.%hu\n" // A = segment + index "M=D\n"; // RAM[segment + index] = D if (!strcmp(vm_instr->arg1, "argument")) { fprintf(fp, pop_indirect_template, ARG, arg2); } else if (!strcmp(vm_instr->arg1, "local")) { fprintf(fp, pop_indirect_template, LCL, arg2); } else if (!strcmp(vm_instr->arg1, "static")) { if (!resolve_static_address(vm_instr, &addr)) { return false; } fprintf(fp, pop_static_template, static_sym_name, addr); } else if (!strcmp(vm_instr->arg1, "this")) { fprintf(fp, pop_indirect_template, THIS, arg2); } else if (!strcmp(vm_instr->arg1, "that")) { fprintf(fp, pop_indirect_template, THAT, arg2); } else if (!strcmp(vm_instr->arg1, "pointer")) { addr = POINTER + vm_instr->arg2; fprintf(fp, pop_addr_template, addr); } else if (!strcmp(vm_instr->arg1, "temp")) { addr = TEMP + vm_instr->arg2; fprintf(fp, pop_addr_template, addr); } else { err("error: invalid segment name \"%s\"\n", vm_instr->arg1); return false; } return true; } static bool write_label(struct vm_instruction_t *vm_instr, FILE *fp) { char label_asm[] = "(%s)\n"; fprintf(fp, label_asm, vm_instr->arg1); return true; } static bool write_goto(struct vm_instruction_t *vm_instr, FILE *fp) { char goto_asm[] = "@%s\n" "0;JMP\n"; fprintf(fp, goto_asm, vm_instr->arg1); return true; } static bool write_if(struct vm_instruction_t *vm_instr, FILE *fp) { char if_asm[] = "@SP\n" // pop register D "AM=M-1\n" "D=M\n" // pop value into D register "@%s\n" "D;JNE\n"; fprintf(fp, if_asm, vm_instr->arg1); return true; } ////////// // // The Elements of Computing Systems, 2nd edition, pg. 214 // // CALLING CONVENTIONS STACK DIAGRAM // =================================== // Low memory addresses // // ... similar blocks above ... // |--------------------| \ // | some value | | Local variables/working stack of _caller_ // |--------------------| | // | some value | | // |--------------------| < -------- BEGIN FUNCTION CALL -------- // ARG -> | argument 0 | | Argument segment of _callee_: // |--------------------| | Pushed by caller before calling // | argument 1 | | callee using 'call' command. // |--------------------| | // | ... | | // |--------------------| < // LCL-5 -> | return address | | Saved frame of _caller_: // |--------------------| | Pushed by the VM when handling // LCL-4 -> | saved LCL | | the 'call' command. // |--------------------| | When handling 'return', the VM // LCL-3 -> | saved ARG | | pops these values and uses them // |--------------------| | for restoring the memory segments // LCL-2 -> | saved THIS | | of, and returning to, the caller's // |--------------------| | code. // LCL-1 -> | saved THAT | | // |--------------------| < // LCL -> | local 0 | | The local segment of _callee_: // |--------------------| | Initialized by the VM when handling // | local 1 | | the 'function' command. // |--------------------| | // | working stack... | | Working stack of _callee_ // |--------------------| < // SP -> | < undefined > | | // +--------------------+ | // _||_ | // direction stack \ / / // grows (up) \/ // // High memory addresses // static bool write_function(struct vm_instruction_t *vm_instr, FILE *fp) { size_t i, num_locals; num_locals = vm_instr->arg2; char set_local_boilerplate[] = "M=0\n" "A=A+1\n"; char set_sp[] = "D=A\n" // D = number of locals "@SP\n" // get address of SP "M=D\n"; // set SP to new value // (functionName) // injects function entry label into the code // repeat nVars times: // nVars = number of local variables // push 0 // initializes local variable to 0 fprintf(fp, "(%s)\n", vm_instr->arg1); // write function label fprintf(fp, "@SP\n"); // get SP for (i = 0; i < num_locals; ++i) { fprintf(fp, "%s", set_local_boilerplate); // write 'push 0' } fprintf(fp, "%s", set_sp); return true; } static bool write_return(FILE *fp) { /* * frame = LCL // frame is a temporary variable * retAddr = *(frame - 5) // put return address in a temporary variable * *ARG = pop() // repositions the return value for the caller * SP = ARG+1 // repositions SP for the caller * THAT = *(frame - 1) // restores THAT for the caller * THIS = *(frame - 2) // restores THIS for the caller * ARG = *(frame - 3) // restores ARG for the caller * LCL = *(frame - 4) // restores LCL for the caller * goto retAddr // jump to where return address points */ char ret_boilerplate[] = "// *ARG = pop()\n" "@SP\n" "AM=M-1\n" // decrement A and SP "D=M\n" // "pop" (read) return value into D "@ARG\n" "A=M\n" // A points to argument segment "M=D\n" // *ARG = D // (D = pop()) "// SP = ARG+1\n" "D=A+1\n" // A still contains arg pointer "@SP\n" "M=D\n" "// frame = LCL\n" "// THAT = *(frame - 1)\n" "@LCL\n" "AM=M-1\n" // decrement A and LCL "D=M\n" // D = *(frame - 1) "@THAT\n" "M=D\n" // THAT = D "// THIS = *(frame - 2)\n" "@LCL\n" "AM=M-1\n" // decrement A and LCL "D=M\n" // D = *(frame - 2) "@THIS\n" "M=D\n" "// ARG = *(frame - 3)\n" "@LCL\n" "AM=M-1\n" // decrement A and LCL "D=M\n" // D = *(frame - 3) "@ARG\n" "M=D\n" "// R13 = retAddr = *(frame - 5)\n" "@LCL\n" "AM=M-1\n" // decrement A and LCL // now LCL = LCL - 4 "D=M-1\n" // D = *(frame - 4 - 1) "@R13\n" "M=D\n" // R13 = D (retAddr) "// LCL = *(frame - 4)\n" "@LCL\n" "A=M\n" // put pointer in address reg. "D=M\n" // D = prev. LCL value "@LCL\n" "M=D\n" // write prev LCL value to LCL "// goto retAddr\n" "@R13\n" // location of retAddr "A=M\n" // A = retAddr "0;JMP\n" // return "\n"; fprintf(fp, "%s", ret_boilerplate); return true; } static bool write_call(struct vm_instruction_t *vm_instr, FILE *fp) { uint16_t new_arg; /* * push retAddr // generates a label and pushes it to the stack * push LCL // saves LCL of caller * push ARG // saves ARG of caller * push THIS // saves THIS of caller * push THAT // saves THAT of caller * ARG = SP - 5 - nArgs // repositions ARG * LCL = SP // repositions LCL * goto functionName // transfers control to the callee * (retAddr) // injects the return address label into the code */ // Note: I use a different convention for generating return address // labels. The book does FilenameFunctionname$ret.<0-n> for n returns, // but the extra bookkeeping will annoy me. So I'll just use the current // line number instead. This works because the function name also // contains the file name, and the file name combined with a line number // provides a uniqueness guarantee, so return addresses won't collide. char call_boilerplate[] = "// push retAddr\n" "@%s.%hu\n" // will format to retAddr "D=A\n" // D = retAddr as constant "@SP\n" "M=M+1\n" // RAM[SP]++ // inc SP "A=M-1\n" // A = RAM[SP] - 1 // prev top "M=D\n" // RAM[SP] = local pointer "// push LCL\n" "@LCL\n" "D=M\n" // D = current local pointer "@SP\n" "M=M+1\n" // RAM[SP]++ // inc SP "A=M-1\n" // A = RAM[SP] - 1 // prev top "M=D\n" // RAM[SP] = arg pointer "// push ARG\n" "@ARG\n" "D=M\n" // D = current arg pointer "@SP\n" "M=M+1\n" // RAM[SP]++ // inc SP "A=M-1\n" // A = RAM[SP] - 1 // prev top "M=D\n" // RAM[SP] = arg "// push THIS\n" "@THIS\n" "D=M\n" // D = current this "@SP\n" "M=M+1\n" // RAM[SP]++ // inc SP "A=M-1\n" // A = RAM[SP] - 1 // prev top "M=D\n" // RAM[SP] = this "// push THAT\n" "@THAT\n" "D=M\n" // D = current that "@SP\n" "M=M+1\n" // RAM[SP]++ // inc SP "A=M-1\n" // A = RAM[SP] - 1 // prev top "M=D\n" // RAM[SP] = that "// ARG = SP - 5 - nArgs\n" "@SP\n" "D=M\n" // D = SP "@%hu\n" // will format to (5 + nArgs) "D=D-A\n" // D = SP - 5 - nArgs "@ARG\n" "M=D\n" "// LCL = SP\n" "@SP\n" "D=M\n" // D = SP "@LCL\n" "M=D\n" // LCL = SP "// goto functionName\n" "@%s\n" "0;JMP\n" "// (retAddr)\n" "(%s.%hu)\n" "\n"; //print_vm_instruction(vm_instr, fp); // TODO remove me new_arg = 5 + vm_instr->arg2; // probably breaks if arg2 > 32K lmfao fprintf(fp, call_boilerplate, vm_instr->arg1, file_line_no, new_arg, vm_instr->arg1, vm_instr->arg1, file_line_no); return true; } bool write_instruction(struct vm_instruction_t *vm_instr, FILE *fp) { fprintf(fp, "\n// %lu: %s\n", file_line_no, vm_instr->line); switch (vm_instr->cmd) { case C_ARITHMETIC: return write_arithmetic(vm_instr, fp); case C_PUSH: return write_push(vm_instr, fp); case C_POP: return write_pop(vm_instr, fp); case C_LABEL: return write_label(vm_instr, fp); case C_GOTO: return write_goto(vm_instr, fp); case C_IF: return write_if(vm_instr, fp); case C_FUNCTION: return write_function(vm_instr, fp); case C_RETURN: return write_return(fp); case C_CALL: return write_call(vm_instr, fp); default: err("error: unrecognized instruction (%u)\n", vm_instr->cmd); return false; } return false; // should never reach here tbh } #endif // _CODEWRITER_H |