7-128
Seiko Epson Corporation
S1C17 CORE MANUAL
(REV. 1.2)
sub.a
%rd, %rs
sub.a/c %rd, %rs
sub.a/nc %rd, %rs
Function
24-bit subtraction
Standard)
rd
(23:0)
←
rd
(23:0) -
rs
(23:0)
Extension 1)
rd
(23:0)
←
rs
(23:0) -
imm13
(zero extended)
Extension 2)
rd
(23:0)
←
rs
(23:0) -
imm24
Code
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 0 1 1 0 0
r d
1 0 1 0
r s
sub.a
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0 0 1 1 0 0
r d
0 0 1 0
r s
sub.a/c
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0 0 1 1 0 0
r d
0 1 1 0
r s
sub.a/nc
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Flag
IL IE C V Z N
– – – – – –
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Mode
Src: Register direct
%rs
=
%r0
to
%r7
Dst: Register direct
%rd
=
%r0
to
%r7
CLK
One cycle
Description
(1) Standard
sub.a %rd,%rs ;
rd
←
rd - rs
The content of the
rs
register is subtracted from the
rd
register.
(2) Extension 1
ext imm13
sub.a %rd,%rs ;
rd
←
rs - imm13
The 13-bit immediate
imm13
is subtracted from the content of the
rs
register after being zero-
extended, and the result is loaded into the
rd
register. The content of the
rs
register is not
altered.
(3) Extension 2
ext imm11
; imm11(10:0) = imm24(23:13)
ext imm13
; = imm24(12:0)
sub.a %rd,%rs ;
rd
←
rs - imm24
The 24-bit immediate
imm24
is subtracted from the content of the
rs
register, and the result is
loaded into the
rd
register. The content of the
rs
register is not altered.
(4) Conditional execution
The
/c
or
/nc
suffix on the opcode specifies conditional execution.
sub.a/c
Executed as
sub.a
when the C flag is 1 or executed as
nop
when the flag is 0
sub.a/nc
Executed as
sub.a
when the C flag is 0 or executed as
nop
when the flag is 1
In this case, the
ext
instruction can be used to extend the operand.
(5) Delayed slot instruction
This instruction may be executed as a delayed slot instruction by writing it directly after
a branch instruction with the “d” bit. In this case, extension of the immediate by the
ext
instruction cannot be performed.
Example
(1)
sub.a %r0,%r0
; r0 = r0 - r0
(2)
ext 0x7ff
ext 0x1fff
sub.a %r1,%r2
; r1 = r2 - 0xffffff