[llvm-dev] How shall I evaluate the latency of each instruction in LLVM IR?
Matt Davis via llvm-dev
llvm-dev at lists.llvm.org
Mon May 13 08:04:34 PDT 2019
It sounds like you might be interested in llvm’s Machine Code Analyzer. It’s an llvm tool that can calculate reciprocal throughput by simulating an out-of-order instruction pipeline. It also provides other useful cycle information:
Your question asks about IR. llvm-mca currently only works on assembly. However, you can easily generate assembly from IR or make use of MCA as a library. I suggest just converting your IR to assembly and running that through llvm-mca.
MCA is built on LLVM instruction scheduling information which contains cycle latency information. If you’re curious of what that data looks like, outside of MCA, take a peek at the X86 instruction scheduling information located around: ‘llvm/lib/Target/X86/X86Schedule.td’
From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Duan Bing via llvm-dev <llvm-dev at lists.llvm.org>
Reply-To: Duan Bing <hibduan at gmail.com>
Date: Sunday, May 12, 2019 at 6:59 PM
To: LLVM Developers Mailing List <llvm-dev at lists.llvm.org>
Subject: [llvm-dev] How shall I evaluate the latency of each instruction in LLVM IR?
Inspired by https://www.agner.org/optimize/instruction_tables.pdf<https://urldefense.proofpoint.com/v2/url?u=https-3A__www.agner.org_optimize_instruction-5Ftables.pdf&d=DwMFaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=UilupKr8sbkenSLlythLNg&m=DWhb3uSjfkI09NsIvzdD_gqnlaI7VN0NpDYUdEvguDw&s=g7xcpplySDXjLzySPYQQjj3BbmDZdSgQtcKxwgCOh9s&e=>, which gives us the latency and reciprocal throughput of each instruction in the different architecture of X86, Is there anybody taking the effort to do a similar job for LLVM IR?
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