ACA Unit 8 Hardware and Software for VLIW and EPIC Notes — Unit 8 – Download as PDF File .pdf), Text File .txt) or read online. G-2 Appendix G Hardware and Software for VLIW and EPIC. In this chapter we discuss compiler technology for increasing the amount of par- allelism that we. View Notes – from ENG at BGS Institute of Technology. | Website for.
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Often NOP instructions are executed for multiple sequential cycles. Generalization of the modulo loop buffer code layout.
The p-bit bit 0 controls whether the next instruction executes in parallel. Assume the compiler determined that ins1 could be safely speculatively executed a second time, but ins2 gliw not. The Trace Family of computers was available in three sizes where each size replicated a cluster. It does, however, specialize instructions so that they are likely to become bit instructions.
In contrast, one VLIW instruction encodes hadrware operations, at least one operation for each execution unit of a device. Please help improve this article by adding citations to reliable sources. The C6X-1 processors can execute from one to eight instructions in parallel. This company, like Multiflow, failed vlie a few years.
Co-design of Compiler and Hardware Techniques to Reduce Program Code Size on a VLIW Processor
Each instruction in an execute packet must use a different functional unit. Since the number of transistors on a chip has grown, the perceived disadvantages of the VLIW have diminished in importance.
The schedule for a single iteration is divided into a sequence of stages, each with a length of II. To accommodate these operation fields, Harxware instructions are usually at least 64 bits wide, and far wider on some architectures.
The branch bit bit 15 controls whether branch instructions or certain S-unit arithmetic and shift instructions are available. Because loops are typically executed more frequently, minimizing loop size improves softwrae utilization of on-chip memories and program caches. The loop body is a single iteration, modulo scheduled software-pipelined loop. Instructions are fetched eight at a time from program softtware in bundles called fetch packets.
Once an epilog stage has been collapsed, the minimum number of iterations that will be completely executed shortest path through loop is reduced by one, from three to two.
Multiple Issue Processors: Superscalar and VLIW – ppt video online download
The remaining seven expansion bits bits are used to specify different variations of the bit instruction set. Archived from the original PDF on Due to the design requirements of a high performance VLIW processor, bit instructions must be kept on a bit boundary.
Suppose it were safe to speculatively execute meaning that it would not cause incorrect program results ins1 one extra time. The control-oriented applications had more pipeline NOP instructions, and the loop-oriented applications had more padding NOP instructions. The register set bit bit 19 indicates which set of eight registers is used for three operand bit instructions. The loop body is demarcated by special instructions. Clearly, software-pipelined loop collapsing and the modulo loop buffer are going to have no effect on the size of control-oriented code.
The effect is that the NOP is issued in parallel with the instruction requiring the latency. Proceedings of the 10th annual international symposium on Computer architecture. He realized that to get good performance and target a wide-issue machine, it would be necessary to find parallelism beyond that generally within a basic block.
This allows it to move and preschedule operations speculatively before the branch is taken, favoring the most likely path it expects through the branch.
Very long instruction word computing Digital signal processing Instruction processing Instruction set architectures Parallel computing.
Example using the branch with parallel NOP instruction. The total schedule length TL is the number of cycles to complete one loop iteration. A latency is the number andd cycles it takes for the effect of an instruction to complete. The automotive benchmarks are dominated by control code, the telecom code is primarily loop-oriented, and the networking algorithms are a mixture of control- and loop-oriented code. We call such instruction specialization tailoring.
When the software-pipelined loop enters the epilog the loop buffer disables the execution of instructions in the order that they were inserted. For example, if a first instruction’s result is used as a second instruction’s input, then they cannot execute at the same time and the second instruction cannot execute before the first.
The compressor does not swap or move instructions outside of execute packets, nor change registers of instructions in order to improve compression.
A hardware loop buffer is a program cache specialized to hold a loop body. All instructions can be optionally guarded by a static predicate.
Multiple Issue Processors: Superscalar and VLIW
The expansion bits and p-bits are effectively extra opcode bits that are hardwate to each instruction in the fetch packet. It uses a similar code density improvement method called configurable long instruction word CLIW.
As a practical matter, this means that the compiler software used to create the final programs becomes far more complex, but the hardware is simpler than in many other means of parallelism.
Each new fetch packet may contain eight bit instructions a regular fetch packetor contain a mixture of and bit instructions a header-based fetch packet. VLIW architectures are growing in popularity, softwwre in the embedded system market, where it is possible to customize a processor for an application in a system-on-a-chip.