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py/asmx64: Change stack management to reference locals by rsp not rbp. 

The rsp register is always a fixed distance below rbp, and using rsp to
reference locals on the stack frees up the rbp register for general purpose
use.
This commit is contained in:
Damien George 2018-10-13 12:49:19 +11:00
parent 11bc38d55f
commit 8941c63290
1 changed files with 33 additions and 30 deletions
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63
py/asmx64.c
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@ -183,21 +183,22 @@ STATIC void asm_x64_write_word32_to(asm_x64_t *as, int offset, int w32) {
*/
STATIC void asm_x64_write_r64_disp(asm_x64_t *as, int r64, int disp_r64, int disp_offset) {
assert(disp_r64 != ASM_X64_REG_RSP);
if (disp_r64 == ASM_X64_REG_R12) {
// special case for r12; not fully implemented
assert(SIGNED_FIT8(disp_offset));
asm_x64_write_byte_3(as, MODRM_R64(r64) | MODRM_RM_DISP8 | MODRM_RM_R64(disp_r64), 0x24, IMM32_L0(disp_offset));
return;
}
if (disp_offset == 0 && disp_r64 != ASM_X64_REG_RBP && disp_r64 != ASM_X64_REG_R13) {
asm_x64_write_byte_1(as, MODRM_R64(r64) | MODRM_RM_DISP0 | MODRM_RM_R64(disp_r64));
uint8_t rm_disp;
if (disp_offset == 0 && (disp_r64 & 7) != ASM_X64_REG_RBP) {
rm_disp = MODRM_RM_DISP0;
} else if (SIGNED_FIT8(disp_offset)) {
asm_x64_write_byte_2(as, MODRM_R64(r64) | MODRM_RM_DISP8 | MODRM_RM_R64(disp_r64), IMM32_L0(disp_offset));
rm_disp = MODRM_RM_DISP8;
} else {
asm_x64_write_byte_1(as, MODRM_R64(r64) | MODRM_RM_DISP32 | MODRM_RM_R64(disp_r64));
rm_disp = MODRM_RM_DISP32;
}
asm_x64_write_byte_1(as, MODRM_R64(r64) | rm_disp | MODRM_RM_R64(disp_r64));
if ((disp_r64 & 7) == ASM_X64_REG_RSP) {
// Special case for rsp and r12, they need a SIB byte
asm_x64_write_byte_1(as, 0x24);
}
if (rm_disp == MODRM_RM_DISP8) {
asm_x64_write_byte_1(as, IMM32_L0(disp_offset));
} else if (rm_disp == MODRM_RM_DISP32) {
asm_x64_write_word32(as, disp_offset);
}
}
@ -529,52 +530,54 @@ void asm_x64_jcc_label(asm_x64_t *as, int jcc_type, mp_uint_t label) {
void asm_x64_entry(asm_x64_t *as, int num_locals) {
assert(num_locals >= 0);
asm_x64_push_r64(as, ASM_X64_REG_RBP);
asm_x64_mov_r64_r64(as, ASM_X64_REG_RBP, ASM_X64_REG_RSP);
num_locals |= 1; // make it odd so stack is aligned on 16 byte boundary
asm_x64_sub_r64_i32(as, ASM_X64_REG_RSP, num_locals * WORD_SIZE);
asm_x64_push_r64(as, ASM_X64_REG_RBX);
asm_x64_push_r64(as, ASM_X64_REG_R12);
asm_x64_push_r64(as, ASM_X64_REG_R13);
num_locals |= 1; // make it odd so stack is aligned on 16 byte boundary
asm_x64_sub_r64_i32(as, ASM_X64_REG_RSP, num_locals * WORD_SIZE);
as->num_locals = num_locals;
}
void asm_x64_exit(asm_x64_t *as) {
asm_x64_sub_r64_i32(as, ASM_X64_REG_RSP, -as->num_locals * WORD_SIZE);
asm_x64_pop_r64(as, ASM_X64_REG_R13);
asm_x64_pop_r64(as, ASM_X64_REG_R12);
asm_x64_pop_r64(as, ASM_X64_REG_RBX);
asm_x64_write_byte_1(as, OPCODE_LEAVE);
asm_x64_pop_r64(as, ASM_X64_REG_RBP);
asm_x64_ret(as);
}
// locals:
// - stored on the stack in ascending order
// - numbered 0 through as->num_locals-1
// - RBP points above the last local
// - RSP points to the first local
//
// | RBP
// v
// | RSP
// v
// l0 l1 l2 ... l(n-1)
// ^ ^
// | low address | high address in RAM
//
STATIC int asm_x64_local_offset_from_ebp(asm_x64_t *as, int local_num) {
return (-as->num_locals + local_num) * WORD_SIZE;
STATIC int asm_x64_local_offset_from_rsp(asm_x64_t *as, int local_num) {
(void)as;
// Stack is full descending, RSP points to local0
return local_num * WORD_SIZE;
}
void asm_x64_mov_local_to_r64(asm_x64_t *as, int src_local_num, int dest_r64) {
asm_x64_mov_mem64_to_r64(as, ASM_X64_REG_RBP, asm_x64_local_offset_from_ebp(as, src_local_num), dest_r64);
asm_x64_mov_mem64_to_r64(as, ASM_X64_REG_RSP, asm_x64_local_offset_from_rsp(as, src_local_num), dest_r64);
}
void asm_x64_mov_r64_to_local(asm_x64_t *as, int src_r64, int dest_local_num) {
asm_x64_mov_r64_to_mem64(as, src_r64, ASM_X64_REG_RBP, asm_x64_local_offset_from_ebp(as, dest_local_num));
asm_x64_mov_r64_to_mem64(as, src_r64, ASM_X64_REG_RSP, asm_x64_local_offset_from_rsp(as, dest_local_num));
}
void asm_x64_mov_local_addr_to_r64(asm_x64_t *as, int local_num, int dest_r64) {
int offset = asm_x64_local_offset_from_ebp(as, local_num);
int offset = asm_x64_local_offset_from_rsp(as, local_num);
if (offset == 0) {
asm_x64_mov_r64_r64(as, dest_r64, ASM_X64_REG_RBP);
asm_x64_mov_r64_r64(as, dest_r64, ASM_X64_REG_RSP);
} else {
asm_x64_lea_disp_to_r64(as, ASM_X64_REG_RBP, offset, dest_r64);
asm_x64_lea_disp_to_r64(as, ASM_X64_REG_RSP, offset, dest_r64);
}
}
@ -587,12 +590,12 @@ void asm_x64_mov_reg_pcrel(asm_x64_t *as, int dest_r64, mp_uint_t label) {
/*
void asm_x64_push_local(asm_x64_t *as, int local_num) {
asm_x64_push_disp(as, ASM_X64_REG_RBP, asm_x64_local_offset_from_ebp(as, local_num));
asm_x64_push_disp(as, ASM_X64_REG_RSP, asm_x64_local_offset_from_rsp(as, local_num));
}
void asm_x64_push_local_addr(asm_x64_t *as, int local_num, int temp_r64) {
asm_x64_mov_r64_r64(as, temp_r64, ASM_X64_REG_RBP);
asm_x64_add_i32_to_r32(as, asm_x64_local_offset_from_ebp(as, local_num), temp_r64);
asm_x64_mov_r64_r64(as, temp_r64, ASM_X64_REG_RSP);
asm_x64_add_i32_to_r32(as, asm_x64_local_offset_from_rsp(as, local_num), temp_r64);
asm_x64_push_r64(as, temp_r64);
}
*/