[llvm-dev] Measuring memory usage of opt passes.

[Anmol Paralkar (anmparal) via llvm-dev]

Hi,



I need to measure the memory usage of opt passes and have some questions in this regard.



First off, this does not really do anything; is it a bug?



$ clang -mllvm -time-passes -mllvm -track-memory -c -O3 ./p0.c

So, instead, I do:


$ clang -emit-llvm -O3 -c ./p0.c

$ opt -time-passes -track-memory ./p0.bc -O3 -o p0.O3.bc 2> p0.O3.txt


Which gets me the report I am looking for, however, I do not understand why there are negative numbers in the Mem column.



===-------------------------------------------------------------------------===

                      ... Pass execution timing report ...

===-------------------------------------------------------------------------===



…



---User Time---   --User+System--   ---Wall Time---  ---Mem---  --- Name ---

0.0010 ( 33.3%)   0.0010 ( 33.3%)   0.0012 ( 41.2%)     324576  Simplify the CFG

…

 0.0000 (  0.0%)   0.0000 (  0.0%)   0.0000 (  0.4%)      -7184  Scalar Evolution Analysis

…

 Also, what are the units for the numbers in the Mem column?



I found the -ftime-report option to clang; is there a similar way to request memory usage tracking of opt passes from clang?

Thank you,
Anmol.
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