[llvm-bugs] [Bug 28832] New: LICM takes forever (100+ seconds) on a small testcase with large number of loads/stores per block

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=28832

            Bug ID: 28832
           Summary: LICM takes forever (100+ seconds) on a small testcase
                    with large number of loads/stores per block
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: dberlin at dberlin.org
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 16871
  --> https://llvm.org/bugs/attachment.cgi?id=16871&action=edit
Small version of testcase

This is the same testcase as PR28670.

I've attached the small version.

On my mac, LICM takes >100 seconds, all of it being spent in the
aliassettracker, doing merges and alias calls:
  52.1751 ( 48.2%)   0.5258 ( 47.6%)  52.7009 ( 48.2%)  53.0047 ( 48.2%)  Loop
Invariant Code Motion
  20.9636 ( 19.4%)   0.2059 ( 18.6%)  21.1694 ( 19.4%)  21.2563 ( 19.3%)  Loop
Invariant Code Motion
  17.6664 ( 16.3%)   0.1026 (  9.3%)  17.7690 ( 16.2%)  17.8337 ( 16.2%)  Loop
Invariant Code Motion

On the larger version of this testcase, it's even worse.

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