Epson S5U1C17001C, Manual

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8-28
EPSOn
S5U1C17001C ManUal
(C COMPilEr PaCkagE fOr S1C17 faMily) (Ver. 1.5.0)
8 aSSEMBlEr
sjr xx
/
xjr xx
instructions
Branch distance = -128 to 126:
The extended instruction is expanded with no
ext
used.
Branch distance = -1,048,576 to -130 or 128 to 1,048,574:
The extended instruction is expanded with one
ext
used.
Branch distance = -16,777,216 to -1,048,578 or 1,048,576 to 16,777,214:
The extended instruction is expanded with two
ext
used.
Note that
ext
instructions may be removed even in a case other than "
ext 0
". In the example below, no
ext
instruction is required since operand 3 will be automatically sign extended if all the bits of operands 1
and 2 and the MSB of operand 3 are 1. In this case, the added
ext
instructions are removed.
Example:
L1:
nop
xjrgt L1 ;
(L1 - branch address - 2) >> 1
→
-2
Before optimization After optimization
nop nop
ext 0x7
←
operand 1 ( imm3 )
jrgt 0x7e
ext 0x1fff
←
operand 2 ( imm13 )
jrgt 0x7c
←
operand 3 ( sign7 )
Optimization 4: for absolute branch instructions (
scalla
/
xcalla
/
sjpa
/
xjpa
instructions)
Example:
sub:
ret
main:
xsub.a %sp,0x4
:
xcalla sub
add.a %sp,0x4
ret
The assembler obtains the destination address (
sub
) from the dump and map files and determines the
number of
ext
instructions to be used directly from the destination address.
Destination address = 0 to 0x7f: The extended instruction is expanded with no
ext
used.
Destination address = 0x80 to 0xfffff: The extended instruction is expanded with one
ext
used.
Destination address = 0xfffff to 0xffffff: The extended instruction is expanded with two
ext
used.
Optimization 5: when the operand is an expression using a symbol
Example:
sub:
ret
main:
xsub.a %sp,0x4
:
xldb %r0,[sub+0x2]
add.a %sp,0x4
ret
The assembler evaluates the expression in the operand and determines the number of
ext
instructions to be
used.
Evaluation result = 0 to 0x7f: The extended instruction is expanded with no
ext
used.
Evaluation result = 0x80 to 0xfffff: The extended instruction is expanded with one
ext
used.
Evaluation result = 0xfffff to 0xffffff: The extended instruction is expanded with two
ext
used.