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[LoopVersioning] Add a check to see if the input loop is in LCSSA form #116443

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[LoopVersioning] Add a check to see if the input loop is in LCSSA form #116443

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Commits on Nov 15, 2024

  1. [LoopVersioning] Add a check to see if the input loop is in LCSSA form 

    Loop Optimizations expect the input loop to be in LCSSA form. But it seems
that LoopVersioning doesn't have any check to see if the loop is actually in
LCSSA form. As a result, if we give it a loop which is not in LCSSA form but
still correct semantically, the resulting transformation fails to pass through
verifier pass with the following error.

Instruction does not dominate all uses!
%inc = add nsw i16 undef, 1
store i16 %inc, ptr @c, align 1

As the loop is not in LCSSA form, LoopVersioning's transformations leads to
invalid IR! As some instructions do not dominate all their uses.

This patch checks if a loop is in LCSSA form, if not it will call
formLCSSARecursively on the loop before passing it to LoopVersioning.

Fixes: llvm#36998
    @VedantParanjape
    VedantParanjape committed Nov 15, 2024
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