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Support local register variables

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Similar to GCC a local asm register variable enforces the use of a
specified register in asm operands (and doesn't otherwise
matter).  Works only if the variable is directly mentioned as
operand.  For that we now generally store a backpointer from
an SValue to a Sym when the SValue was the result of unary()
parsing a symbol identifier.
This commit is contained in:
Michael Matz
2016-10-06 04:05:30 +02:00
parent 3bc9c325c5
commit f081acbfba
4 changed files with 58 additions and 6 deletions
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33
i386-asm.c
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@ -1185,6 +1185,28 @@ static const char *skip_constraint_modifiers(const char *p)
return p;
}
/* If T (a token) is of the form "%reg" returns the register
number and type, otherwise return -1. */
ST_FUNC int asm_parse_regvar (int t)
{
const char *s;
Operand op;
if (t < TOK_IDENT)
return -1;
s = table_ident[t - TOK_IDENT]->str;
if (s[0] != '%')
return -1;
t = tok_alloc(s+1, strlen(s)-1)->tok;
unget_tok(t);
unget_tok('%');
parse_operand(tcc_state, &op);
/* Accept only integer regs for now. */
if (op.type & OP_REG)
return op.reg;
else
return -1;
}
#define REG_OUT_MASK 0x01
#define REG_IN_MASK 0x02
@ -1227,6 +1249,11 @@ ST_FUNC void asm_compute_constraints(ASMOperand *operands,
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);
}
@ -1274,6 +1301,12 @@ ST_FUNC void asm_compute_constraints(ASMOperand *operands,
} 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) {