Commit Graph

4 Commits

Author SHA1 Message Date
Rafael Ávila de Espíndola 7b44f0428a Add a llvm::shuffle and use it in lld
With this --shuffle-sections=seed produces the same result in every
host.

Reviewed By: grimar, MaskRay

Differential Revision: https://reviews.llvm.org/D74971
2020-02-22 10:05:29 -08:00
Fangrui Song 878159038b [ELF][test] Fix --symbol-ordering-file tests of shuffle_sections.s 2020-02-19 17:13:06 -08:00
Fangrui Song 40463301e4 [ELF][test] Fix shuffle_sections.s
C++ standard libraries have different random function implementations.
We cannot expect a particular order.
2020-02-19 17:10:32 -08:00
Rafael Ávila de Espíndola d48d339156 [lld][ELF] Add --shuffle-sections=seed to shuffle input sections
Summary:
This option causes lld to shuffle sections by assigning different
priorities in each run.

The use case for this is to introduce randomization in benchmarks. The
idea is inspired by the paper "Producing Wrong Data Without Doing
Anything Obviously Wrong!"
(https://www.inf.usi.ch/faculty/hauswirth/publications/asplos09.pdf). Unlike
the paper, we shuffle individual sections, not just input files.

Doing this in lld is particularly convenient as the --reproduce option
makes it easy to collect all the necessary bits for relinking the
program being benchmarked. Once that it is done, all that is needed is
to add --shuffle-sections=0 to the response file and relink before each
run of the benchmark.

Differential Revision: https://reviews.llvm.org/D74791
2020-02-19 13:44:12 -08:00