[LLVMbugs] [Bug 20641] New: Codegen Compile Time increase after r211900

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=20641

            Bug ID: 20641
           Summary: Codegen Compile Time increase after r211900
           Product: tools
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: llc
          Assignee: unassignedbugs at nondot.org
          Reporter: bruno.cardoso at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 12888
  --> http://llvm.org/bugs/attachment.cgi?id=12888&action=edit
Codegen-only compile time for each separated source code

As mentioned in llvmdev
(https://groups.google.com/forum/#!topic/llvm-dev/9B2j3LKEF0I), commit r211900
introduced compile time regression:

    Re-apply r211287: Remove support for LLVM runtime multi-threading.
...
    git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211900

I reproduced the problem by reverting the patch and extracting codegen only
compile time for each separated source code (10x run for each source). Bellow
the top 5 (sorted by descending total time), the rest is attached.

cpp,CodeGen Compile Time Increase (User), Total time FE+BE (sec)
bullet-btSoftBody.cpp,1.15565,2.1502
bullet-BenchmarkDemo.cpp,1.13269,1.1308
bullet-btDiscreteDynamicsWorld.cpp,1.16331,0.7851
bullet-btSoftBodyHelpers.cpp,1.12274,0.5422
bullet-btSequentialImpulseConstraintSolver.cpp,1.17394,0.5338

Command line example:
$ /usr/bin/clang -DNO_TIME -c -Xclang -emit-codegen-only -I
/Users/bruno/Dev/srcs/test-suite/MultiSource/Benchmarks/Bullet/include
/Users/bruno/Dev/srcs/test-suite/MultiSource/Benchmarks/Bullet/btSoftBody.cpp
-O3 -o /tmp/x.o

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