8000 Basic native ARM emitter · sparkfun/circuitpython@fe3d16e · GitHub
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Basic native ARM emitter
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‎py/asmarm.c

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/*
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* This file is part of the Micro Python project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2013, 2014 Fabian Vogt
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include <stdio.h>
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#include <assert.h>
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#include <string.h>
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#include "mpconfig.h"
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#include "misc.h"
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#include "asmarm.h"
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// wrapper around everything in this file
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#if MICROPY_EMIT_ARM
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#define SIGNED_FIT24(x) (((x) & 0xff800000) == 0) || (((x) & 0xff000000) == 0xff000000)
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struct _asm_arm_t {
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uint pass;
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uint code_offset;
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uint code_size;
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byte *code_base;
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byte dummy_data[4];
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uint max_num_labels;
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int *label_offsets;
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int num_locals;
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uint push_reglist;
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uint stack_adjust;
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};
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asm_arm_t *asm_arm_new(uint max_num_labels) {
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asm_arm_t *as;
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as = m_new0(asm_arm_t, 1);
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as->max_num_labels = max_num_labels;
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as->label_offsets = m_new(int, max_num_labels);
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return as;
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}
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void asm_arm_free(asm_arm_t *as, bool free_code) {
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if (free_code) {
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m_del(byte, as->code_base, as->code_size);
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}
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m_del_obj(asm_arm_t, as);
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}
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void asm_arm_start_pass(asm_arm_t *as, uint pass) {
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as->pass = pass;
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as->code_offset = 0;
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if (pass == ASM_ARM_PASS_COMPUTE) {
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memset(as->label_offsets, -1, as->max_num_labels * sizeof(int));
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}
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}
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void asm_arm_end_pass(asm_arm_t *as) {
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if (as->pass == ASM_ARM_PASS_COMPUTE) {
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// calculate size of code in bytes
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as->code_size = as->code_offset;
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as->code_base = m_new(byte, as->code_size);
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}
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}
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// all functions must go through this one to emit bytes
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// if as->pass < ASM_ARM_PASS_EMIT, then this function only returns a buffer of 4 bytes length
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STATIC byte *asm_arm_get_cur_to_write_bytes(asm_arm_t *as, int num_bytes_to_write) {
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if (as->pass < ASM_ARM_PASS_EMIT) {
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as->code_offset += num_bytes_to_write;
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return as->dummy_data;
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} else {
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assert(as->code_offset + num_bytes_to_write <= as->code_size);
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byte *c = as->code_base + as->code_offset;
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as->code_offset += num_bytes_to_write;
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return c;
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}
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}
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uint asm_arm_get_code_size(asm_arm_t *as) {
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return as->code_size;
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}
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void *asm_arm_get_code(asm_arm_t *as) {
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return as->code_base;
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}
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// Insert word into instruction flow
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STATIC void emit(asm_arm_t *as, uint op) {
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*(uint*)asm_arm_get_cur_to_write_bytes(as, 4) = op;
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}
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// Insert word into instruction flow, add "ALWAYS" condition code
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STATIC void emit_al(asm_arm_t *as, uint op) {
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emit(as, op | ARM_CC_AL);
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}
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// Basic instructions without condition code
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STATIC uint asm_arm_op_push(uint reglist) {
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// stmfd sp!, {reglist}
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return 0x92d0000 | (reglist & 0xFFFF);
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}
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STATIC uint asm_arm_op_pop(uint reglist) {
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// ldmfd sp!, {reglist}
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return 0x8bd0000 | (reglist & 0xFFFF);
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}
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STATIC uint asm_arm_op_mov_reg(uint rd, uint rn) {
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// mov rd, rn
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return 0x1a00000 | (rd << 12) | rn;
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}
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STATIC uint asm_arm_op_mov_imm(uint rd, uint imm) {
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// mov rd, #imm
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return 0x3a00000 | (rd << 12) | imm;
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}
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STATIC uint asm_arm_op_mvn_imm(uint rd, uint imm) {
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// mvn rd, #imm
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return 0x3e00000 | (rd << 12) | imm;
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}
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STATIC uint asm_arm_op_add_imm(uint rd, uint rn, uint imm) {
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// add rd, rn, #imm
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return 0x2800000 | (rn << 16) | (rd << 12) | (imm & 0xFF);
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}
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STATIC uint asm_arm_op_add_reg(uint rd, uint rn, uint rm) {
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// add rd, rn, rm
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return 0x0800000 | (rn << 16) | (rd << 12) | rm;
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}
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STATIC uint asm_arm_op_sub_imm(uint rd, uint rn, uint imm) {
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// sub rd, rn, #imm
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return 0x2400000 | (rn << 16) | (rd << 12) | (imm & 0xFF);
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}
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void asm_arm_bkpt(asm_arm_t *as) {
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// bkpt #0
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emit_al(as, 0x1200070);
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}
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// locals:
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// - stored on the stack in ascending order
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// - numbered 0 through as->num_locals-1
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// - SP points to first local
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//
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// | SP
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// v
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// l0 l1 l2 ... l(n-1)
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// ^ ^
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// | low address | high address in RAM
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void asm_arm_entry(asm_arm_t *as, int num_locals) {
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if (num_locals < 0) {
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num_locals = 0;
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}
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as->stack_adjust = 0;
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as->num_locals = num_locals;
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as->push_reglist = 1 << REG_R1 | 1 << REG_R2 | 1 << REG_R3 | 1 << REG_R4
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| 1 << REG_R5 | 1 << REG_R6 | 1 << REG_R7 | 1 << REG_R8;
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// Only adjust the stack if there are more locals than usable registers
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if(num_locals > 3) {
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as->stack_adjust = num_locals * 4;
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// Align stack to 8 bytes
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if(as->num_locals & 1)
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as->stack_adjust += 4;
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}
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emit_al(as, asm_arm_op_push(as->push_reglist | 1 << REG_LR));
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if (as->stack_adjust > 0) {
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emit_al(as, asm_arm_op_sub_imm(REG_SP, REG_SP, as->stack_adjust));
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}
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}
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void asm_arm_exit(asm_arm_t *as) {
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if (as->stack_adjust > 0) {
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emit_al(as, asm_arm_op_add_imm(REG_SP, REG_SP, as->stack_adjust));
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}
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emit_al(as, asm_arm_op_pop(as->push_reglist | (1 << REG_PC)));
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}
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void asm_arm_label_assign(asm_arm_t *as, uint label) {
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assert(label < as->max_num_labels);
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if (as->pass < ASM_ARM_PASS_EMIT) {
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// assign label offset
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assert(as->label_offsets[label] == -1);
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as->label_offsets[label] = as->code_offset;
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} else {
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// ensure label offset has not changed from PASS_COMPUTE to PASS_EMIT
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assert(as->label_offsets[label] == as->code_offset);
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}
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}
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void asm_arm_align(asm_arm_t* as, uint align) {
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// TODO fill unused data with NOPs?
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as->code_offset = (as->code_offset + align - 1) & (~(align - 1));
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}
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void asm_arm_data(asm_arm_t* as, uint bytesize, uint val) {
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byte *c = asm_arm_get_cur_to_write_bytes(as, bytesize);
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// only write to the buffer in the emit pass (otherwise we overflow dummy_data)
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if (as->pass == ASM_ARM_PASS_EMIT) {
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// little endian
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for (uint i = 0; i < bytesize; i++) {
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*c++ = val;
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val >>= 8;
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}
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}
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}
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void asm_arm_mov_reg_reg(asm_arm_t *as, uint reg_dest, uint reg_src) {
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emit_al(as, asm_arm_op_mov_reg(reg_dest, reg_src));
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}
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void asm_arm_mov_reg_i32(asm_arm_t *as, uint rd, int imm) {
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// TODO: There are more variants of immediate values
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if ((imm & 0xFF) == imm) {
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emit_al(as, asm_arm_op_mov_imm(rd, imm));
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} else if (imm < 0 && ((-imm) & 0xFF) == -imm) {
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emit_al(as, asm_arm_op_mvn_imm(rd, -imm));
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} else {
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//Insert immediate into code and jump over it
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emit_al(as, 0x59f0000 | (rd << 12)); // ldr rd, [pc]
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emit_al(as, 0xa000000); // b pc
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emit(as, imm);
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}
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}
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void asm_arm_mov_local_reg(asm_arm_t *as, int local_num, uint rd) {
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// str rd, [sp, #local_num*4]
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emit_al(as, 0x58d0000 | (rd << 12) | (local_num << 2));
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}
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void asm_arm_mov_reg_local(asm_arm_t *as, uint rd, int local_num) {
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// ldr rd, [sp, #local_num*4]
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emit_al(as, 0x59d0000 | (rd << 12) | (local_num << 2));
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}
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void asm_arm_cmp_reg_i8(asm_arm_t *as, uint rd, int imm) {
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// cmp rd, #imm
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emit_al(as, 0x3500000 | (rd << 16) | (imm & 0xFF));
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}
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void asm_arm_cmp_reg_reg(asm_arm_t *as, uint rd, uint rn) {
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// cmp rd, rn
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emit_al(as, 0x1500000 | (rd << 16) | rn);
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}
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void asm_arm_less_op(asm_arm_t *as, uint rd, uint rn) {
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asm_arm_cmp_reg_reg(as, rd, rn); // cmp rd, rn
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emit(as, asm_arm_op_mov_imm(REG_RET, 1) | ARM_CC_LT); // movlt REG_RET, #1
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emit(as, asm_arm_op_mov_imm(REG_RET, 0) | ARM_CC_GE); // movge REG_RET, #0
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}
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void asm_arm_add_reg(asm_arm_t *as, uint rd, uint rn, uint rm) {
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// add rd, rn, rm
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emit_al(as, asm_arm_op_add_reg(rd, rn, rm));
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}
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void asm_arm_mov_reg_local_addr(asm_arm_t *as, uint rd, int local_num) {
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// add rd, sp, #local_num*4
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emit_al(as, asm_arm_op_add_imm(rd, REG_SP, local_num << 2));
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}
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void asm_arm_bcc_label(asm_arm_t *as, int cond, uint label) {
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assert(label < as->max_num_labels);
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int dest = as->label_offsets[label];
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int rel = dest - as->code_offset;
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rel -= 8; // account for instruction prefetch, PC is 8 bytes ahead of this instruction
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rel >>= 2; // in ARM mode the branch target is 32-bit aligned, so the 2 LSB are omitted
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if (SIGNED_FIT24(rel)) {
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emit(as, cond | 0xa000000 | (rel & 0xffffff));
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} else {
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printf("asm_arm_bcc: branch does not fit in 24 bits\n");
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}
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}
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void asm_arm_b_label(asm_arm_t *as, uint label) {
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asm_arm_bcc_label(as, ARM_CC_AL, label);
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}
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void asm_arm_bl_ind(asm_arm_t *as, void *fun_ptr, uint fun_id, uint reg_temp) {
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// If the table offset fits into the ldr instruction
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if(fun_id < (0x1000 / 4)) {
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emit_al(as, asm_arm_op_mov_reg(REG_LR, REG_PC)); // mov lr, pc
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emit_al(as, 0x597f000 | (fun_id << 2)); // ldr pc, [r7, #fun_id*4]
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return;
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}
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emit_al(as, 0x59f0004 | (reg_temp << 12)); // ldr rd, [pc, #4]
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// Set lr after fun_ptr
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emit_al(as, asm_arm_op_add_imm(REG_LR, REG_PC, 4)); // add lr, pc, #4
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emit_al(as, asm_arm_op_mov_reg(REG_PC, reg_temp)); // mov pc, reg_temp
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emit(as, (uint) fun_ptr);
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}
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#endif // MICROPY_EMIT_ARM

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