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(andcosts): Modify costs to match the hardware, and add 

explanatory comments.

From-SVN: r9245
This commit is contained in:
Jim Wilson 1995-03-29 13:58:12 -08:00
parent 71851aaa7c
commit a6f71af520
1 changed files with 13 additions and 5 deletions
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18
gcc/config/sh/sh.c
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@ -1400,16 +1400,24 @@ andcosts (RTX)
rtx RTX;
{
int i;
/* Anding with a register is a single cycle and instruction. */
if (GET_CODE (XEXP (RTX, 1)) != CONST_INT)
return 2;
return 1;
i = INTVAL (XEXP (RTX, 1));
/* And can use the extend insns cheaply. */
/* These constants are single cycle extu.[bw] instructions. */
if (i == 0xff || i == 0xffff)
return 1;
/* Constants that can be used in an and immediate instruction is a single
cycle, but this requires r0, so make it a little more expensive. */
if (CONST_OK_FOR_L (i))
return 2;
/* Any small constant is reasonably cheap - but requires r0. */
/* Constants that can be loaded with a mov immediate and an and.
This case is probably unnecessary. */
if (CONST_OK_FOR_I (i))
return 3;
return 5;
return 2;
/* Any other constants requires a 2 cycle pc-relative load plus an and.
This case is probably unnecessary. */
return 3;
}
/* Return the cost of a multiply. */