swiftlang/swift

[SR-7148] Compile-time conditionalization of endianness in the compiler should be done by target checking

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#49,696 opened on Mar 8, 2018

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bugcompilergood first issue

Description
Previous ID SR-7148
Radar None
Original Reporter @jckarter
Type Bug
Votes 0
Component/s Compiler
Labels Bug, StarterBug
Assignee None
Priority Medium

md5: 7f26b7e8c0700431c7bacc1871180f85

Issue Description:

IRGen appears to have grown compile-time conditionalizations on host properties, e.g.:

https://github.com/apple/swift/blob/master/lib/IRGen/GenEnum.cpp#L3892

This is not correct if cross-compiling for a target with different endianness than the compiler host. This should check the properties of the target instead of being a #if

Contributor guide

Tech stack
cpp
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C++compiler internalscross compilationendianness
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65
Research direction
Examine GenEnum.cpp line 3892 to see the compile time conditional on endianness. Investigate how the target's endianness can be accessed in IRGen. Look for examples in the codebase where target properties are used instead of host conditionals. Implement a change to use target endianness check.