functionality difference-performance postgreSQLv14-GCC-llvm-clang

[arjun shetty <arjunshetty955@xxxxxxxxx>]

Hi,

PostgreSQLv14- compiled with LLVM-Clangv13 and GCCv11,And captured performance using HammerDBv4.3-TPC-H.
And Observed the functionality differences as LLVM-Clangv13-triggers heapgetpage instead XidInMVCCSnapshot or vice versa with GCC.
I would like to know here the functionality differences triggered i.e. function call "heapgetpage vs XidInMVCCSnapshot '' in GCC vs LLVM-Clangv13
And also observed the performance difference GCC performing (Query execution time (small value is better) better than LLVM-Clang 13 on same BareMetal with same H/W and DB configurations

 perf data top hot functions:
 LLVM-Clangv13:

=============
 TPCH-Query-completed-50.526 seconds
 
 Overhead    Symbol
  19.41%    [.] tts_buffer_heap_getsomeattrs
  17.75%    [.] heapgetpage
   9.46%    [.] bpchareq
   5.86%    [.] ExecEvalScalarArrayOp
   5.85%    [.] ExecInterpExpr
   4.50%    [.] ReadBuffer_common
   3.02%    [.] heap_getnextslot
   
   GCCv11
  =======
   
   TPCH-Query-completed-41.593 seconds

  21.13%            [.] tts_buffer_heap_getsomeattrs
  11.58%            [.] XidInMVCCSnapshot
  10.87%            [.] bpchareq
   7.07%            [.] ExecEvalScalarArrayOp
   5.93%            [.] ExecInterpExpr
   5.16%            [.] ReadBuffer_common
   3.61%            [.] heapgetpage

Regards

Arjun