Basic native ARM emitter

1 files changed, 326 insertions, 0 deletions

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