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[X86] Lower calls with rv_marker attribute.
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Authored by fhahn on Wed, Jan 13, 6:11 AM.



This patch adds support for lowering function calls with the
rv_marker attribute. The goal is to expand such calls to the
following sequence of instructions:

CALL{32,64} @fn
movl %ebp, %ebp

This sequence of instructions triggers Objective-C runtime optimizations,
hence we want to ensure no instructions get moved in between them.
This patch achieves that by adding a new CALL_RVMARKER ISD node,
which gets turned into the CALL{32,64}_RVMARKER pseudo, which eventually gets
expanded into the sequence mentioned above. The sequence is then marked
as instruction bundle, to avoid anything being moved in between.

@ahatanak is working on using this attribute in the front- & middle-end.

Together with the front- & middle-end changes, this should address
PR31925 for X86.

This is the X86 version of 46bc40e50246c1902a1ca7916c8286cb837643ee,
which added similar support for AArch64.

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Event Timeline

fhahn created this revision.Wed, Jan 13, 6:11 AM
fhahn requested review of this revision.Wed, Jan 13, 6:11 AM
Herald added a project: Restricted Project. · View Herald TranscriptWed, Jan 13, 6:11 AM
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fhahn added a comment.Wed, Jan 13, 6:20 AM

I am not too familiar with how calls are handled in the X86 backend. I would really appreciate any pointers to cases that this approach might miss.

This is only relevant for Objective-C code on X86, so it would probably be OK to drop support for the CALL32* variants?

RKSimon resigned from this revision.Thu, Jan 14, 2:06 AM
RKSimon added a reviewer: pengfei.
skan added a subscriber: skan.Mon, Jan 18, 6:07 PM