Answer:
A. After the following code executes, what value is in register $7 ?
addiu $5,$0,-25
addiu $6,$0,25
slt $7,$5,$6
Register $7 will be set to 1, because
(when the patterns in registers $5 and $6 are regarded as signed values)
$5 < $6.
B. After the following code executes, what value is in register $7 ?
addiu $5,$0,-25
addiu $6,$0,25
sltu $7,$5,$6
Register $7 will be set to 0, because
(when the patterns in registers $5 and $6 are regarded as unsigned values)
$5 is not less than $6.
If the bit pattern in register $5 is regarded as unsigned, it looks like a
large positive value.
Set on Less Than Immediate
The
other two set instructions compare an operand
register with an immediate value in the instruction.
There is a version for two's complement:
# $s and imm contain two's comp. integers
# -32768 <= imm <= 32767
#
slti d,s,imm # if ( $s < imm )
# d = 1
# else
# d = 0
And a version for unsigned integers:
# $s and imm contain unsigned integers
# 0 <= imm <= 32767
#
sltiu d,s,imm # if ( $s < imm )
# d = 1
# else
# d = 0
#
In both, the immediate field of the machine instruction is 16 bits wide.
However, the sltiu instruction can only be used with
small integers 0 <= imm <= 32767 (and another range which is
not important for this course.)
QUESTION 4:
After the following code executes, what value is in register $7 ?
addiu $6,$0,25
slti $7,$6,37
