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[SR-6271] Unable to emit assembly from swift compiler to multiple files #48821

alblue opened this issue Nov 1, 2017 · 2 comments

[SR-6271] Unable to emit assembly from swift compiler to multiple files #48821

alblue opened this issue Nov 1, 2017 · 2 comments


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@alblue alblue commented Nov 1, 2017

Previous ID SR-6271
Radar None
Original Reporter @alblue
Type Bug
Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, Driver
Assignee None
Priority Medium

md5: bb3071f2e46457be531dc5b7605524bf

relates to:

  • SR-327 Add --outdir argument to swiftc

Issue Description:

When compiling multiple Swift files (because they have inter-relationships between them, for example) it's not possible to get the assembly written out to a file. The only output possibility is to stdout.

This command will print out the assembly of the file to stdout:

swiftc -module-name example -emit-assembly main.swift dependency.swift

However, if you try and get it to write to separate files, it doesn't because multiple -o files are not permitted:

swiftc -module-name example -emit-assembly main.swift -o main.s dependency.swift -o dependency.s
error: cannot specify -o when generating multiple output files

Normally with clang this would be taken care of simply by passing -S (which is also the same for the swift compiler) and the output would be written to <filename>.s for each individual file. However, for -S in swiftc, it assumes that you want to write to stdout:

case FrontendOptions::EmitAssembly: {
if (Opts.OutputFilenames.empty())
Suffix = "s";

What I'd like to do is be able to generate individual files, or be allowed to have a means of disabling the automatic-stdout option for the -emit phases (probably the same for ll as well). This would require either an additional option that disables this option, or have a means to allow a per-file output when multiple source files are used.

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Contributor Author

@alblue alblue commented Nov 1, 2017

One possible implementation: allow for -o - even in the presence of multiple input files (similar to waht happens today) and then allow -S to write to a .s file.

Another possible implementation: allow another flag to say -dont-use-stdout-for-emit-options, which would just set the suffix.

Not sure which one is least worse, really.

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@belkadan belkadan commented Nov 1, 2017

You can use an output file map for this.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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