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[patch] PR21734 fix





The updating of phi-nodes in the loop-peeling utils in the vectorizer did
not take into account the possibility that invariant (and dead) phis of the
following form could be present in the loop:
   m2 = phi <init: m15, latch: m15>
(there are no defs of m in the loop).
As observed by Jeff, because 'm' is not being defined in the loop, it does
not have a 'current_def', which results in generating the following phi in
the duplicated loop:
  m20 = phi <init: m15, latch: NULL>
which later leads to an ICE when trying to rename this variable in the
duplicated loop.

The following patch fixes that by setting the missing phi-arg to the
phi-result:
  m20 = phi <init: m15, latch: m20>

Bootstrapped and tested on powerpc-apple-darwin.

ok for mainline?

Changelogs:

        PR tree-optimization/21734
        * tree-vectorizer.c (slpeel_update_phis_for_duplicate_loop): Use
the
        phi_result when current_def is not available.
        (slpeel_update_phi_nodes_for_guard1): Don't fail if current_def is
not
        available.

        PR tree-optimization/21734
        * g++.dg/vect/pr21734_1.cc: New.
        * g++.dg/vect/pr21734_2.cc: New.

Patch:

(See attached file: pr21734.patch)

Attachment: pr21734.patch
Description: Binary data


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