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optimize the generated code when save_reg is required

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Before this patch, save_reg can't reuse the temporary local variable
created before to save register. It may consume a lot of stack memory. this patch make save_reg reuse the temporary local variable.
This commit is contained in:
Pursuer 2019-01-10 03:32:23 +08:00
parent 0c313f491b
commit b3b685d92a
1 changed files with 63 additions and 3 deletions
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66
tccgen.c
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@ -70,6 +70,14 @@ ST_DATA struct switch_t {
int def_sym; /* default symbol */
} *cur_switch; /* current switch */
#define MAX_TEMP_LOCAL_VARIABLE_NUMBER 0x4
/*list of temporary local variables on the stack in current function. */
ST_DATA struct temp_local_variable {
int location; //offset on stack. Svalue.c.i
short size;
short align;
} arr_temp_local_vars[MAX_TEMP_LOCAL_VARIABLE_NUMBER];
short nb_temp_local_vars;
/* ------------------------------------------------------------------------- */
static void gen_cast(CType *type);
@ -97,6 +105,8 @@ static int gvtst(int inv, int t);
static void gen_inline_functions(TCCState *s);
static void skip_or_save_block(TokenString **str);
static void gv_dup(void);
static int get_temp_local_var(int size,int align);
static void clear_temp_local_var_list();
ST_INLN int is_float(int t)
{
@ -1033,10 +1043,10 @@ ST_FUNC void save_reg_upstack(int r, int n)
type = &int_type;
#endif
size = type_size(type, &align);
loc = (loc - size) & -align;
l=get_temp_local_var(size,align);
sv.type.t = type->t;
sv.r = VT_LOCAL | VT_LVAL;
sv.c.i = loc;
sv.c.i = l;
store(r, &sv);
#if defined(TCC_TARGET_I386) || defined(TCC_TARGET_X86_64)
/* x86 specific: need to pop fp register ST0 if saved */
@ -1051,7 +1061,6 @@ ST_FUNC void save_reg_upstack(int r, int n)
store(p->r2, &sv);
}
#endif
l = loc;
saved = 1;
}
/* mark that stack entry as being saved on the stack */
@ -1134,6 +1143,56 @@ ST_FUNC int get_reg(int rc)
return -1;
}
/* find a free temporary local variable (return the offset on stack) match the size and align. If none, add new temporary stack variable*/
static int get_temp_local_var(int size,int align){
int i;
struct temp_local_variable *temp_var;
int found_var;
SValue *p;
int r;
char free;
char found;
found=0;
for(i=0;i<nb_temp_local_vars;i++){
temp_var=&arr_temp_local_vars[i];
if(temp_var->size<size||align!=temp_var->align){
continue;
}
/*check if temp_var is free*/
free=1;
for(p=vstack;p<=vtop;p++) {
r=p->r&VT_VALMASK;
if(r==VT_LOCAL||r==VT_LLOCAL){
if(p->c.i==temp_var->location){
free=0;
break;
}
}
}
if(free){
found_var=temp_var->location;
found=1;
break;
}
}
if(!found){
loc = (loc - size) & -align;
if(nb_temp_local_vars<MAX_TEMP_LOCAL_VARIABLE_NUMBER){
temp_var=&arr_temp_local_vars[i];
temp_var->location=loc;
temp_var->size=size;
temp_var->align=align;
nb_temp_local_vars++;
}
found_var=loc;
}
return found_var;
}
static void clear_temp_local_var_list(){
nb_temp_local_vars=0;
}
/* move register 's' (of type 't') to 'r', and flush previous value of r to memory
if needed */
static void move_reg(int r, int s, int t)
@ -7169,6 +7228,7 @@ static void gen_function(Sym *sym)
gfunc_prolog(&sym->type);
local_scope = 0;
rsym = 0;
clear_temp_local_var_list();
block(NULL, NULL, 0);
if (!(nocode_wanted & 0x20000000)
&& ((func_vt.t & VT_BTYPE) == VT_INT)