Re: Okay, who made scalar replacement of aggregates work?

[reza at apple dot com]

I  compiled your suggested program and I found no structure field is assigned to
a registers.  What options did you use ? If it is not too hard for you, cold you send me
the .s file that your compiler generates which assigns structure fields to registers.

Thanks
Reza Yazdani


From: Daniel Berlin <dan@cgsoftware.com>
Date: Thu Jun 07, 2001  09:25:30  AM US/Pacific
To: gcc@gcc.gnu.org
Subject: Okay, who made scalar replacement of aggregates work?


I was told we only do it if the entire class fits in a register.

This is no longer true.


We'll do it to single members of classes/structs now to.

In other words, we do full scalar replacement of aggregates.


Try the following (for C):


typedef enum { APPLE, BANANA, ORANGE } VARIETY;
typedef enum { LONG, ROUND } SHAPE;
typedef struct fruit {
VARIETY variety;
SHAPE shape;
int fred;
int george;
int a;
int b;
int c;
int d;
}
FRUIT;
char * Red="red";
char * Yellow = "yellow";
char *Orange = "orange";

int george (CurrentFruit)
FRUIT *CurrentFruit;
{
return CurrentFruit->george;
}
char *color (CurrentFruit)
FRUIT *CurrentFruit;
{

switch (CurrentFruit->variety) {
case APPLE: return Red;
break;
case BANANA: return Yellow;
break;
case ORANGE: return Orange;
}
}
main( )
{
FRUIT snack;
snack.variety = APPLE;
snack.shape = ROUND;
snack.fred = 30;
snack.george = 3;
printf("%s\n", color (&snack));
printf("%d\n", george (&snack));
}


Even though snack can't fit in a register, some of it's components
will, and we sure as hell put them there.

Make snack as big as you like. We'll still do the repacements we can.


Same with the C++ version.


extern "C" int printf(const char *, ...);
enum VARIETY
{ APPLE, BANANA, ORANGE };
enum SHAPE { LONG, ROUND };
class FRUIT
{
public:
enum VARIETY variety;
enum SHAPE shape;
int george;
int fred;
int a;
int b;
int c;
int d;
};

char * Red="red";
char * Yellow = "yellow";
char *Orange = "orange";

char *color (FRUIT *CurrentFruit)
{

switch (CurrentFruit->variety) {
case APPLE: return Red;
break;
case BANANA: return Yellow;
break;
case ORANGE: return Orange;
}
}
int main( )
{
FRUIT snack;
snack.variety = APPLE;
snack.shape = ROUND;
snack.george = 5;
snack.fred = 30;
printf("%s\n", color (&snack));
printf("%d\n", snack.fred);
}



--Dan
--
"It's a good thing we have gravity, or else when birds died
they'd just stay right up there.  Hunters would be all confused.
"-Steven Wright