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arm-asm: Implement asm_compute_constraints

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Danny Milosavljevic 2021-01-01 17:30:50 +01:00
parent 795d7d5ce6
commit 9a460d3234
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arm-asm.c
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@ -1330,11 +1330,297 @@ ST_FUNC void asm_gen_code(ASMOperand *operands, int nb_operands,
}
}
/* return the constraint priority (we allocate first the lowest
numbered constraints) */
static inline int constraint_priority(const char *str)
{
int priority, c, pr;
/* we take the lowest priority */
priority = 0;
for(;;) {
c = *str;
if (c == '\0')
break;
str++;
switch(c) {
case 'l': // in ARM mode, that's an alias for 'r' [ARM].
case 'r': // register [general]
case 'p': // valid memory address for load,store [general]
pr = 3;
break;
case 'M': // integer constant for shifts [ARM]
case 'I': // integer valid for data processing instruction immediate
case 'J': // integer in range -4095...4095
case 'i': // immediate integer operand, including symbolic constants [general]
case 'm': // memory operand [general]
case 'g': // general-purpose-register, memory, immediate integer [general]
pr = 4;
break;
default:
tcc_error("unknown constraint '%c'", c);
pr = 0;
}
if (pr > priority)
priority = pr;
}
return priority;
}
static const char *skip_constraint_modifiers(const char *p)
{
/* Constraint modifier:
= Operand is written to by this instruction
+ Operand is both read and written to by this instruction
% Instruction is commutative for this operand and the following operand.
Per-alternative constraint modifier:
& Operand is clobbered before the instruction is done using the input operands
*/
while (*p == '=' || *p == '&' || *p == '+' || *p == '%')
p++;
return p;
}
#define REG_OUT_MASK 0x01
#define REG_IN_MASK 0x02
#define is_reg_allocated(reg) (regs_allocated[reg] & reg_mask)
ST_FUNC void asm_compute_constraints(ASMOperand *operands,
int nb_operands, int nb_outputs,
const uint8_t *clobber_regs,
int *pout_reg)
{
/* overall format: modifier, then ,-seperated list of alternatives; all operands for a single instruction must have the same number of alternatives */
/* TODO: Simple constraints
whitespace ignored
o memory operand that is offsetable
V memory but not offsetable
< memory operand with autodecrement addressing is allowed. Restrictions apply.
> memory operand with autoincrement addressing is allowed. Restrictions apply.
n immediate integer operand with a known numeric value
E immediate floating operand (const_double) is allowed, but only if target=host
F immediate floating operand (const_double or const_vector) is allowed
s immediate integer operand whose value is not an explicit integer
X any operand whatsoever
0...9 (postfix); (can also be more than 1 digit number); an operand that matches the specified operand number is allowed
*/
/* TODO: ARM constraints:
k the stack pointer register
G the floating-point constant 0.0
Q memory reference where the exact address is in a single register ("m" is preferable for asm statements)
R an item in the constant pool
S symbol in the text segment of the current file
[ Uv memory reference suitable for VFP load/store insns (reg+constant offset)]
[ Uy memory reference suitable for iWMMXt load/store instructions]
Uq memory reference suitable for the ARMv4 ldrsb instruction
*/
ASMOperand *op;
int sorted_op[MAX_ASM_OPERANDS];
int i, j, k, p1, p2, tmp, reg, c, reg_mask;
const char *str;
uint8_t regs_allocated[NB_ASM_REGS];
/* init fields */
for (i = 0; i < nb_operands; i++) {
op = &operands[i];
op->input_index = -1;
op->ref_index = -1;
op->reg = -1;
op->is_memory = 0;
op->is_rw = 0;
}
/* compute constraint priority and evaluate references to output
constraints if input constraints */
for (i = 0; i < nb_operands; i++) {
op = &operands[i];
str = op->constraint;
str = skip_constraint_modifiers(str);
if (isnum(*str) || *str == '[') {
/* this is a reference to another constraint */
k = find_constraint(operands, nb_operands, str, NULL);
if ((unsigned) k >= i || i < nb_outputs)
tcc_error("invalid reference in constraint %d ('%s')",
i, str);
op->ref_index = k;
if (operands[k].input_index >= 0)
tcc_error("cannot reference twice the same operand");
operands[k].input_index = i;
op->priority = 5;
} else if ((op->vt->r & VT_VALMASK) == VT_LOCAL
&& op->vt->sym
&& (reg = op->vt->sym->r & VT_VALMASK) < VT_CONST) {
op->priority = 1;
op->reg = reg;
} else {
op->priority = constraint_priority(str);
}
}
/* sort operands according to their priority */
for (i = 0; i < nb_operands; i++)
sorted_op[i] = i;
for (i = 0; i < nb_operands - 1; i++) {
for (j = i + 1; j < nb_operands; j++) {
p1 = operands[sorted_op[i]].priority;
p2 = operands[sorted_op[j]].priority;
if (p2 < p1) {
tmp = sorted_op[i];
sorted_op[i] = sorted_op[j];
sorted_op[j] = tmp;
}
}
}
for (i = 0; i < NB_ASM_REGS; i++) {
if (clobber_regs[i])
regs_allocated[i] = REG_IN_MASK | REG_OUT_MASK;
else
regs_allocated[i] = 0;
}
/* sp cannot be used */
regs_allocated[13] = REG_IN_MASK | REG_OUT_MASK;
/* fp cannot be used yet */
regs_allocated[11] = REG_IN_MASK | REG_OUT_MASK;
/* allocate registers and generate corresponding asm moves */
for (i = 0; i < nb_operands; i++) {
j = sorted_op[i];
op = &operands[j];
str = op->constraint;
/* no need to allocate references */
if (op->ref_index >= 0)
continue;
/* select if register is used for output, input or both */
if (op->input_index >= 0) {
reg_mask = REG_IN_MASK | REG_OUT_MASK;
} else if (j < nb_outputs) {
reg_mask = REG_OUT_MASK;
} else {
reg_mask = REG_IN_MASK;
}
if (op->reg >= 0) {
if (is_reg_allocated(op->reg))
tcc_error
("asm regvar requests register that's taken already");
reg = op->reg;
goto reg_found;
}
try_next:
c = *str++;
switch (c) {
case '=': // Operand is written-to
goto try_next;
case '+': // Operand is both READ and written-to
op->is_rw = 1;
/* FALL THRU */
case '&': // Operand is clobbered before the instruction is done using the input operands
if (j >= nb_outputs)
tcc_error("'%c' modifier can only be applied to outputs",
c);
reg_mask = REG_IN_MASK | REG_OUT_MASK;
goto try_next;
case 'l': // In non-thumb mode, alias for 'r'--otherwise r0-r7 [ARM]
case 'r': // general-purpose register
case 'p': // loadable/storable address
/* any general register */
for (reg = 0; reg <= 8; reg++) {
if (!is_reg_allocated(reg))
goto reg_found;
}
goto try_next;
reg_found:
/* now we can reload in the register */
op->is_llong = 0;
op->reg = reg;
regs_allocated[reg] |= reg_mask;
break;
case 'I': // integer that is valid as an data processing instruction immediate (0...255, rotated by a multiple of two)
case 'J': // integer in the range -4095 to 4095 [ARM]
case 'K': // integer that satisfies constraint I when inverted (one's complement)
case 'L': // integer that satisfies constraint I when inverted (two's complement)
case 'i': // immediate integer operand, including symbolic constants
if (!((op->vt->r & (VT_VALMASK | VT_LVAL)) == VT_CONST))
goto try_next;
break;
case 'M': // integer in the range 0 to 32
if (!
((op->vt->r & (VT_VALMASK | VT_LVAL | VT_SYM)) ==
VT_CONST))
goto try_next;
break;
case 'm': // memory operand
case 'g':
/* nothing special to do because the operand is already in
memory, except if the pointer itself is stored in a
memory variable (VT_LLOCAL case) */
/* XXX: fix constant case */
/* if it is a reference to a memory zone, it must lie
in a register, so we reserve the register in the
input registers and a load will be generated
later */
if (j < nb_outputs || c == 'm') {
if ((op->vt->r & VT_VALMASK) == VT_LLOCAL) {
/* any general register */
for (reg = 0; reg <= 8; reg++) {
if (!(regs_allocated[reg] & REG_IN_MASK))
goto reg_found1;
}
goto try_next;
reg_found1:
/* now we can reload in the register */
regs_allocated[reg] |= REG_IN_MASK;
op->reg = reg;
op->is_memory = 1;
}
}
break;
default:
tcc_error("asm constraint %d ('%s') could not be satisfied",
j, op->constraint);
break;
}
/* if a reference is present for that operand, we assign it too */
if (op->input_index >= 0) {
operands[op->input_index].reg = op->reg;
operands[op->input_index].is_llong = op->is_llong;
}
}
/* compute out_reg. It is used to store outputs registers to memory
locations references by pointers (VT_LLOCAL case) */
*pout_reg = -1;
for (i = 0; i < nb_operands; i++) {
op = &operands[i];
if (op->reg >= 0 &&
(op->vt->r & VT_VALMASK) == VT_LLOCAL && !op->is_memory) {
for (reg = 0; reg <= 8; reg++) {
if (!(regs_allocated[reg] & REG_OUT_MASK))
goto reg_found2;
}
tcc_error("could not find free output register for reloading");
reg_found2:
*pout_reg = reg;
break;
}
}
/* print sorted constraints */
#ifdef ASM_DEBUG
for (i = 0; i < nb_operands; i++) {
j = sorted_op[i];
op = &operands[j];
printf("%%%d [%s]: \"%s\" r=0x%04x reg=%d\n",
j,
op->id ? get_tok_str(op->id, NULL) : "",
op->constraint, op->vt->r, op->reg);
}
if (*pout_reg >= 0)
printf("out_reg=%d\n", *pout_reg);
#endif
}
ST_FUNC void asm_clobber(uint8_t *clobber_regs, const char *str)