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[MSAN] Convert ActualFnStart to be a particular Instruction *, not BB
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Authored by guiand on Aug 14 2020, 11:27 AM.

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Summary
This allows us to add addtional instrumentation before the function start,
without splitting the first BB. Removes the BB splitting for KMSAN's prologue.

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Event Timeline

guiand created this revision.Aug 14 2020, 11:27 AM
Herald added a project: Restricted Project. · View Herald TranscriptAug 14 2020, 11:27 AM
guiand requested review of this revision.Aug 14 2020, 11:27 AM
guiand added a reviewer: vitalybuka.
eugenis added inline comments.Aug 14 2020, 12:04 PM
llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
1097–1098

Could you also change insertKmsanPrologue to get rid of BB splitting?
I'm thinking set ActualFnStart = F.getEntryBlock().getFirstNonPHI() in advance, then simply insert all the KMSan stuff into IRBuilder<>(ActualFnStart).

guiand updated this revision to Diff 285750.Aug 14 2020, 1:29 PM
guiand edited the summary of this revision. (Show Details)

Remove BB splitting for KMSAN

eugenis accepted this revision.Aug 14 2020, 1:48 PM

LGTM

This revision is now accepted and ready to land.Aug 14 2020, 1:48 PM
guiand updated this revision to Diff 285755.Aug 14 2020, 2:00 PM

Move removeUnreachableBlocks before inserting the prologue. This makes sure there's no issue with the ActualFnStart instruction being deleted before the visitor loop.

eugenis accepted this revision.Aug 14 2020, 2:38 PM

LGTM++