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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Further improvement can be achieved by executing instructions in an order different from that in which they occur in a program, termed out-of-order execution. A latency is the number of cycles it takes for the effect of an instruction to complete.
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Very long instruction word
Contemporary VLIWs usually have four to eight main execution units. This company, like Multiflow, failed after a few years.
Back-end compiler and assembler flow depicting the compression of instructions. Trace scheduling is such a method, and involves scheduling the rpic likely path of basic blocks first, inserting compensating code to deal with speculative motions, scheduling the second most likely trace, and so on, until the schedule is complete.
The execute packet boundary is determined by a bit in each instruction called the parallel-bit or p-bit. Because cache activity occurs for data items that are never used, data cache performance and power efficiency are negatively impacted.
These results are softwars upper bound since they assume that all software-pipelined loops can fit in the loop buffer.
Example of a generalized loop scheduled without software pipelining. It has 32 static general-purpose registers, partitioned into two register files.
If the result of an arithmetic operation overflows, then the result saturates to a maximum value, and if an operation underflows, it saturates to a minimum value. When the value of the register n is non-zero, the branch is taken. In this paper we describe the co-design of compiler optimizations and processor architecture features that have progressively reduced code size across three generations of a VLIW processor.
Instruction fetch packet layout showing p-bits. Because ILP must be explicitly expressed in the program vlid, VLIW compiler optimizations often replicate instructions, increasing code size. Because loops are typically executed more frequently, minimizing loop size improves the utilization of on-chip memories and program caches.
Clearly, the MLB reduces code size and improves power efficiency by eliminating the overlapped copies of the instructions in the loop body. Principles, Techniques, and Tools.
Multiple Issue Processors: Superscalar and VLIW – ppt video online download
The compressor runs after the assembly phase and is responsible for converting as many bit instructions as possible to equivalent bit instructions. Transmeta addressed this issue by including a binary-to-binary software compiler layer termed code morphing in their Crusoe implementation of the x86 architecture.
Execution of a modulo scheduled loop. The C includes the C67 floating point instructions. The loop buffer performs the branch automatically.
This was inspired partly by the difficulty Fisher observed at Yale of compiling for architectures like Floating Point Systems ‘ FPS, which had a complex instruction set computing CISC architecture that separated instruction initiation from the instructions that saved the result, needing very complex scheduling algorithms.
Only the kernel code is explicitly represented. We proposed a loop buffer specialized to improve the performance of software-pipelined loops specifically in the following areas Control-oriented code, which contains more branches, saw a larger improvement. Patent 7,, March Example of software-pipelined loop with one epilog stage collapsed.
Notes for Advanced Computer Architecture – ACA by Tarini Mishra
In the above schedule, very little parallelism has been exploited because ins1ins2and ins3 must execute in order within the given loop iteration. Unlike software-pipelined loop collapsing, the MLB reduces code size without requiring instruction speculation.
The compiler does not make the final decision whether an instruction will become a bit instruction. The advantage of kernel-only code is that there is no code growth. However, EPIC architecture is sometimes distinguished from a pure VLIW architecture, since EPIC advocates full instruction predication, rotating register files, and a very long instruction word that can encode non-parallel instruction groups.
The instructions executed parameter measures the number of instructions executed. In contrast, the VLIW method depends on the programs providing all the decisions regarding which instructions to execute simultaneously and how to resolve conflicts. The loop body is demarcated by special instructions.