[cfe-commits] r125183 - in /cfe/trunk: include/clang/AST/ include/clang/Basic/ lib/AST/ lib/CodeGen/ lib/Sema/ lib/StaticAnalyzer/Checkers/ tools/libclang/

[John McCall]

On Feb 9, 2011, at 3:56 PM, Ted Kremenek wrote:
> Was there a noticeable impact on compile-time?  Memory use?

"Before my patch" is r125182.  "After my patch" is r125185.  All measurements except one are the median of 3 approximately similar results as generated on a not-very-reliable, not-hardly-quiescent laptop.

Cocoa_h.m creates 35700 Stmts/Exprs and 85258 Decls.  On a 64-bit platform, this is a theoretical memory savings of 285,600 bytes for Stmts/Exprs and 682,064 bytes for Decls.
  - Before my patch, it allocated 13,008,896 bytes, of which it used 12,449,976, with the remainder being lost to e.g. alignment padding.
    A Release build completed 1000 runs (I'm not sure why I did 1000 runs) on my machine with the following characteristics:
    daysthatwere:clang rjmccall$ runN 1000 ../../Release/bin/clang -fsyntax-only INPUTS/Cocoa_h.m
    name	  avg  	  min  	  med  	  max  	   SD  	 total 
    user	 0.3246	 0.3215	 0.3247	 0.3328	 0.0014	324.5585
    sys	 0.0771	 0.0662	 0.0819	 0.0898	 0.0068	77.1401
    wall	 0.4064	 0.3954	 0.4088	 0.4440	 0.0071	406.4173

  - After my patch, it allocated 12,779,520 bytes, of which it used 12,164,576.  This is a memory savings of 284,400 bytes (used).  1,328,392 bytes of Stmt/Expr nodes were allocated overall.
    A Release build completed 100 runs on my machine with the following characteristics:
    daysthatwere:clang rjmccall$ runN 100 ../../Release/bin/clang -fsyntax-only INPUTS/Cocoa_h.m
    name	  avg  	  min  	  med  	  max  	   SD  	 total 
    user	 0.3175	 0.3147	 0.3172	 0.3247	 0.0019	31.7507
    sys	 0.0770	 0.0682	 0.0780	 0.0895	 0.0061	 7.6987
    wall	 0.3994	 0.3886	 0.3990	 0.4162	 0.0073	39.9351


all_std_headers.cpp creates 69666 Stmts/Exprs and 35101 Decls.  On a 64-bit platform, this is a theoretical memory savings of 557,328 bytes for Stmts/Exprs and 280,808 bytes for Decls.
  - Before my patch, it allocated 12,705,792 bytes, of which it used 12,174,357.
    A Release build completed 100 runs on my machine with the following characteristics:
    daysthatwere:clang rjmccall$ runN 100 ../../Release/bin/clang -fsyntax-only INPUTS/all-std-headers.cpp 
    name	  avg  	  min  	  med  	  max  	   SD  	 total 
    user	 0.3725	 0.3692	 0.3727	 0.3765	 0.0015	37.2507
    sys	 0.0474	 0.0394	 0.0480	 0.0463	 0.0056	 4.7440
    wall	 0.4237	 0.4131	 0.4261	 0.4322	 0.0065	42.3729

  - After my patch, it allocated 12,214,272 bytes, of which it used 11,618,501.  This is a memory savings of 555,856 bytes (used).  2,917,712 bytes of Stmt/Expr nodes were allocated overall.
    A Release build completed 100 runs on my machine with the following characteristics:
    daysthatwere:clang rjmccall$ runN 100 ../../Release/bin/clang -fsyntax-only INPUTS/all-std-headers.cpp 
    name	  avg  	  min  	  med  	  max  	   SD  	 total 
    user	 0.3684	 0.3657	 0.3672	 0.3705	 0.0017	36.8390
    sys	 0.0431	 0.0358	 0.0410	 0.0522	 0.0078	 4.3079
    wall	 0.4160	 0.4069	 0.4119	 0.4265	 0.0086	41.5987

So if I didn't completely kill any scientific validity with biased selection in my efforts to get around quiescence problems, this is a modest optimization in running time and a fairly significant optimization of memory usage.  Of course, processing headers only stresses the creation of an AST, not queries against it, so (say) a static-analyzer benchmark might be worthwhile.

John.
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