[PATCH] D36800: Add rewrite by-reference parameter pass

[Tobias Grosser via Phabricator via llvm-commits]

grosser created this revision.
grosser added a project: Polly.
Herald added a subscriber: mgorny.

This pass detangles induction variables from functions, which take variables by
reference. Most fortran functions compiled with gfortran pass variables by
reference. Unfortunately a common pattern, printf calls of induction variables,
prevent in this situation the promotion of the induction variable to a register,
which again inhibits any kind of loop analysis. To work around this issue
we developed a specialized pass which introduces separate alloca slots for
known-read-only references, which indicate the mem2reg pass that the induction
variables can be promoted to registers and consquently enable SCEV to work.

We currently hardcode the information that a function
_gfortran_transfer_integer_write does not read its second parameter, as
dragonegg does not add the right annotations and we cannot change old dragonegg
releases. Hopefully flang will produce the right annotations.


https://reviews.llvm.org/D36800

Files:
  include/polly/LinkAllPasses.h
  lib/CMakeLists.txt
  lib/Support/RegisterPasses.cpp
  lib/Transform/Canonicalization.cpp
  lib/Transform/RewriteByReferenceParameters.cpp
  test/RewriteByReferenceParameters/fortran_io.ll

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