[llvm-bugs] [Bug 32531] New: Load hoisting of indirect loads

via llvm-bugs llvm-bugs at lists.llvm.org
Wed Apr 5 02:35:38 PDT 2017


            Bug ID: 32531
           Summary: Load hoisting of indirect loads
           Product: Polly
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Optimizer
          Assignee: polly-dev at googlegroups.com
          Reporter: llvm at meinersbur.de
                CC: llvm-bugs at lists.llvm.org

Created attachment 18226
  --> http://bugs.llvm.org/attachment.cgi?id=18226&action=edit

Invariant-load-hoisting pre-loads values before the execution of the SCoP
itself to avoid loading the same value several times and also to make
parameters (like array size) available in the isl sets/maps.

Currently, we cannot load-hoist from pointers that by themselves are defined
within the SCoP, but are themselves invariant. Load-hoisting of invariant
pointers could repeat up to an arbitrary depth.

In the attached example (provided by Roman Gareev) no SCoP is detected because
the loop bound %tmp11 is defined within the SCoP. But it should be invariant,
so could be load-hoisted. However, it is loaded from another pointer
%ref.i.i.i.i.i.i.i.i which itself is a load within the SCoP which should be

Since invariant-load-hoisting is already implemented (Using the
-polly-invariant-load-hoisting), it "only" also needs to be applied recursively
to load-hoisted pointers.

@Roman: If you want to implement this yourself, please claim this bug.

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