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[RISCV] Remove support for the unratified Zbt extension.
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Authored by craig.topper on Sep 13 2022, 9:25 PM.

Details

Summary

This extension does not appear to be on its way to ratification.

Out of the unratified bitmanip extensions, this one had the
largest impact on the compiler.

Posting this patch to start a discussion about whether we should
remove these extensions. We'll talk more at the RISC-V sync meeting this
Thursday.

Diff Detail

Event Timeline

craig.topper created this revision.Sep 13 2022, 9:25 PM
Herald added a project: Restricted Project. · View Herald TranscriptSep 13 2022, 9:25 PM
craig.topper requested review of this revision.Sep 13 2022, 9:25 PM
Herald added projects: Restricted Project, Restricted Project. · View Herald TranscriptSep 13 2022, 9:25 PM
craig.topper edited the summary of this revision. (Show Details)

I agree that we should remove support for unratified extension.

asb accepted this revision.Sep 20 2022, 4:40 AM

There seemed to be consensus on this in last week's meeting, and there's no upstream activity on the spec, so removing zbt makes sense to me.

llvm/docs/ReleaseNotes.rst
115

"Support for the"

This revision is now accepted and ready to land.Sep 20 2022, 4:40 AM
reames accepted this revision.Sep 20 2022, 1:52 PM

LGTM as well.

llvm/test/CodeGen/RISCV/ssub_sat_plus.ll