[llvm-bugs] [Bug 39625] New: combining addressing modes increases compile time significantly for the testcase

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=39625

            Bug ID: 39625
           Summary: combining addressing modes increases compile time
                    significantly for the testcase
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: wmi at google.com
                CC: llvm-bugs at lists.llvm.org

Recently we run into a compile time problem when we compiled a target. I got a
synthetic testcase to reproduce the problem. For the problematic testcase, most
of the compile time was spent on FillPlaceholders and InsertPlaceholders
functions. After disabing combing different complex addr modes, the problem
went away.

To reproduce the problem:

$ time -p ~/workarea/llvm-r345241/rbuild/bin/llc -O3 < 1.ll > /tmp/1.s
real 38.16
user 37.99
sys 0.16

$ time -p ~/workarea/llvm-r344255/rbuild/bin/llc -O3
-disable-complex-addr-modes < 1.ll > /tmp/1.s
real 6.68
user 6.56
sys 0.11

Note: The larger the 1.ll is, the more serious the problem. However, I cannot
upload file larger than 1M because of the attachment size limit. For the actual
case, without complex-addr-modes, the compilation took 60s, with
complex-addr-modes, it took >1000s.

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