Method and system for scheduling delay slot in very-long instruction word structure

Abstract

The invention discloses a method and a system for scheduling a delay slot in a very-long instruction word structure. The method comprises the steps of locally scheduling instructions in a current basic block; after the local scheduling is finished, judging whether a residual instruction delay slot exists, if not, ending the scheduling, otherwise, putting an instruction which can be filled into the instruction delay slot and is high in spending into a local standby instruction cache; globally scheduling instructions in a basic block of a branch target, selecting an instruction which can be filled into the instruction delay slot and placing the instruction in a global standby instruction cache; and selecting an instruction from the local standby instruction cache and/or the global standby instruction cache and filling the instruction into the residual instruction delay slot. The system comprises a local scheduling unit, a global scheduling unit and a balanced scheduling unit. According to the method and the system for scheduling the delay slot in the very-long instruction word structure disclosed by the invention, through balance between scheduling of the delay slot and program parallelism, as well as balance between local scheduling and global scheduling, high execution efficiency of programs can be implemented.

Description

technical field [0001] The invention relates to an instruction scheduling technology, in particular to a delay slot scheduling method and system thereof under a super long instruction word structure. Background technique [0002] Very Long Instruction Word (VLIW for short) is a very long instruction combination, which connects many instructions together to increase the speed of operation. VLIW technology is one of the main performances to improve processor instruction-level parallelism. It uses software and hardware to jointly develop processor parallelism. The assembly of long instructions is completed by the compiler instead of using a superscalar processor based on hardware dynamic scheduling strategy, thus greatly reducing hardware complexity and chip power consumption. [0003] In the design of digital signal processor (Digital Signal Processing, referred to as DSP) architecture, research is usually carried out in combination with VILW technology under the reduced inst...

AI Technical Summary

Problems solved by technology

If there is no suitable instruction in the basic block to choose from, then fill in the empty operation instruction, and the global scheduling is to select the appropriate instruction from other basic blocks based on certain constraint rules after finding that there is no suitable instruction in the basic block to fill the delay slot. Instructions are filled, that is to say, global scheduling allows code movement across basic block boundaries. If this process also fails, then select no-op instructions for filling, but the cost of implementing global scheduling on the compiler is relatively high, and it directly affects compilation. Compiler speed

[0005] In traditional DSP processor architecture design, usually only local scheduling algorithm is used or limited to the trade-off between global scheduling and compiler efficiency for compilation speed considerations, while local scheduling algorithm is usually limited to optional target instructions for local function fragments The number is very small, when the compiler is fully optimized, the logical enhancement between instructions in the local function fragment leads to low delay slot usage

When the traditional DSP processor architecture design scheme is not used in the architecture based on VLIW technology, the impact on the parallelism of instructions cannot be evaluated, and the use of delay slots may cause damage to the parallelism of instructions. actual efficiency of the program

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