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openedon Aug 14, 2016
The benchmarks in crate matrixmultiply version 0.1.8 degrade with MIR enabled. (commit bluss/matrixmultiply@3d83647)
Tested using rustc 1.12.0-nightly (1deb02ea6 2016-08-12).
Typical output:
// -C target-cpu=native
test mat_mul_f32::m127 ... bench: 2,703,773 ns/iter (+/- 636,432)
// -Z orbit=off -C target-cpu=native
test mat_mul_f32::m127 ... bench: 648,817 ns/iter (+/- 22,379)
Sure, the matrix multiplication kernel uses some major muckery that it expects the compiler to optimize down and autovectorize, but since it technically is a regression, it gets a report.
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Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues.Area: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.htmlIssue: Problems and improvements with respect to performance of generated code.High priorityRelevant to the compiler team, which will review and decide on the PR/issue.Performance or correctness regression from stable to beta.