Syntax
subf $s_reg1, $s_reg2, $d_reg
subf $d_reg/$s_reg1, $s_reg2
Description
Subtract F_floating subtracts the contents of $s_reg2 from the contents of $s_reg1 or $d_reg and places the result into $d_reg. When the difference of the two operands is exactly 0, the difference has a positive sign for all rounding modes except round toward minus infinity (-¥). For that rounding mode, the difference has a negative sign.
Qualifiers
The following table describes the qualifiers for the subf instructions:
| Instruction | Qualifier description |
| no qualifier | VAX Rounding Mode: Normal rounding |
| VAX Trap Mode: Imprecise, underflow disabled | |
| subfc | VAX Rounding Mode: Chopped |
| subfu | VAX Trap Mode: Imprecise, underflow enabled |
| subfuc | Combined meanings of subfc and subfu |
| subfs | VAX Trap Mode: Software, underflow disabled |
| subfsc | Combined meanings of subfs and subfc |
| subfsu | VAX Trap Mode: Software, underflow enabled |
| subfsuc | Combined meanings of subfs and subfuc |