branch delay slot การใช้

• Both architectures define branch delay slots in order to utilize these fetched instructions.
• Many early RISC designs also shared the characteristic of having a branch delay slot.
• A branch delay slot is an instruction space immediately following a jump or branch.
• Another technique is a branch delay slot.
• The goal of a breakpoints on instructions as well as stepping while debugging within branch delay slot.
• RISC-V omits a branch delay slot because it complicates multicycle CPUs, superscalar CPUs, and long pipelines.
• Because they use branch delay slots, fetched just one instruction per cycle, and execute in-order, there is no performance loss.
• The compilers were designed to keep the processors as full as possible by reducing the number of branch delay slots, and did a particularly good job of it.
• Many RISC designs have included a branch delay slot, a position after a branch instruction that can be filled with an instruction which is executed whether or not the branch is taken.
• Nowadays the branch delay slot is considered an unfortunate side effect of a particular strategy for implementing some RISC designs, and modern RISC designs generally do away with it ( such as PowerPC and more recent versions of SPARC and MIPS ).
• The ideal number of branch delay slots in a particular pipeline implementation is dictated by the number of pipeline stages, the presence of register forwarding, what stage of the pipeline the branch conditions are computed, whether or not a branch target buffer ( BTB ) is used and many other factors.
• This makes conditional branches a problem, because the compiler has to fill the instruction following a conditional branch ( the so-called " branch delay slot " ), with something selected to be " safe " ( i . e ., not dependent on the outcome of the conditional ).