Final answer:
In a 5-stage MIPS pipeline with full forwarding, the presented instruction sequence has no hazards that cannot be resolved with forwarding. To eliminate stalls, the code can be rearranged so that dependent instructions are separated by an independent one, enabling continuous pipeline flow without stalls.
Step-by-step explanation:
The question pertains to identifying and resolving data hazards in a MIPS processor with a 5-stage pipeline using full forwarding. Considering full forwarding, data hazards occur when a subsequent instruction depends on the result of a previous instruction that has not yet completed its execution. In the given sequence of instructions:
- lw $t0, 0($a0)
- addi $t0, $t0, 1
- sw $t0, 0($a0)
- addi $a0, $a0, 4
a. There are no data hazards that cannot be resolved with forwarding because the MIPS pipeline with full forwarding supports resolving hazards between the write-back (WB) stage of an instruction and the execution (EX) stage of the following instruction.
b. To eliminate stalls, the code could be written as follows:
- lw $t0, 0($a0)
- addi $a0, $a0, 4
- addi $t0, $t0, 1
- sw $t0, -4($a0)
By inserting the addi $a0, $a0, 4 instruction after the load, we remove the hazard that would have been caused by the store instruction writing to memory before the increment of the address in the register $a0 occurs. In this way, the pipeline optimization is achieved without stalls.