llvm/llvm-project

[flang] Feature request: support for -Os/-Oz

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#62,268 opened on Apr 20, 2023

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enhancementflang:driverhelp wanted

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Description

flang-new version 17.0.0 (12426441ea2a9fdfcf6121a0061fa91d6112781d)

While building some SPEC CPU 2017 benchmarks, I noticed that Flang doesn't support -Os/-Oz.

Using a simple 'hello world' program:

$ ~/.local/llvm-install/bin/flang-new -Os hello.f90 -o hello
error: invalid integral value 's' in '-Os'

$ ~/.local/llvm-install/bin/flang-new -Oz hello.f90 -o hello
error: invalid integral value 'z' in '-Oz'

Is there a plan for adding support for code size optimization flags in the compiler?

Contributor guide

Research direction
Investigate how flang new currently handles optimization flags like O1/ O2/ O3 and extend that logic to support Os and Oz. Look at the clang driver for reference on how Os/ Oz are mapped to optimization settings.
Tech stack
cpp
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++LLVM basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65