[LLVMbugs] [Bug 15540] New: GVN Compile time 10% regression caused by revision 176408

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=15540

            Bug ID: 15540
           Summary: GVN Compile time 10% regression caused by revision
                    176408
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Core LLVM classes
          Assignee: unassignedbugs at nondot.org
          Reporter: yi.jiang.llvm at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Here is how we build the compiler,
1) We check out source revision 176407 and revision 176408 from trunk.
2) We configure and build the compiler.

The example is originated from TraverseSchema.cpp in 483.xalancbmk (SEPC2006)

We first generate -O0 .bc file and apply two opt respectively. Please see the
attachment common.ll.

$OPT  -Os common.bc --time-passes -o /dev/null

Here is the  result: 
r176407 

   ---User Time---   --System Time--   --User+System--   ---Wall Time---  ---
Name ---
   0.1039 ( 14.7%)   0.0006 (  2.3%)   0.1045 ( 14.3%)   0.1044 ( 14.3%) 
Global Value Numbering

r176408
   ---User Time---   --System Time--   --User+System--   ---Wall Time---  ---
Name ---
   0.1170 ( 16.2%)   0.0006 (  2.4%)   0.1176 ( 15.7%)   0.1175 ( 15.7%) 
Global Value Numbering


It shows more than 10% regression on this case.

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