Optimizing compile time

[Akanksha]

Hi all

I compiled my code with g++ in the verbose mode and got the following
Execution time split

Execution times (seconds)
 garbage collection    :   0.77 ( 0%) usr   0.00 ( 0%) sys   0.77
( 0%) wall
 cfg construction      :   0.34 ( 0%) usr   0.01 ( 0%) sys   0.37
( 0%) wall
 cfg cleanup           :   0.08 ( 0%) usr   0.00 ( 0%) sys   0.08
( 0%) wall
 trivially dead code   :   0.41 ( 0%) usr   0.02 ( 0%) sys   0.43
( 0%) wall
 life analysis         :   1.23 ( 0%) usr   0.01 ( 0%) sys   1.22
( 0%) wall
 life info update      :   0.17 ( 0%) usr   0.00 ( 0%) sys   0.17
( 0%) wall
 alias analysis        :   0.51 ( 0%) usr   0.01 ( 0%) sys   0.53
( 0%) wall
 register scan         :   0.40 ( 0%) usr   0.01 ( 0%) sys   0.42
( 0%) wall
 rebuild jump labels   :   0.13 ( 0%) usr   0.00 ( 0%) sys   0.13
( 0%) wall
 preprocessing         :   0.43 ( 0%) usr   0.18 ( 4%) sys   0.78
( 0%) wall
 parser                :   4.73 ( 1%) usr   1.03 (23%) sys  58.17
( 9%) wall
 name lookup           :   0.90 ( 0%) usr   0.87 (20%) sys   1.53
( 0%) wall
 expand                :   3.07 ( 1%) usr   0.33 ( 8%) sys   3.39
( 1%) wall
 varconst              :   0.01 ( 0%) usr   0.01 ( 0%) sys   0.03
( 0%) wall
 integration           :   5.76 ( 1%) usr   0.44 (10%) sys   6.19
( 1%) wall
 jump                  :   0.12 ( 0%) usr   0.00 ( 0%) sys   0.09
( 0%) wall
 CSE                   :  75.38 (13%) usr   0.05 ( 1%) sys  75.43
(11%) wall
 loop analysis         :   0.37 ( 0%) usr   0.00 ( 0%) sys   0.38
( 0%) wall
 branch prediction     :   0.49 ( 0%) usr   0.03 ( 1%) sys   0.52
( 0%) wall
 flow analysis         :   0.07 ( 0%) usr   0.00 ( 0%) sys   0.07
( 0%) wall
 combiner              : 466.97 (78%) usr   0.04 ( 1%) sys 467.08
(70%) wall
 local alloc           :  25.46 ( 4%) usr   0.05 ( 1%) sys  25.53
( 4%) wall
 global alloc          :   3.52 ( 1%) usr   1.28 (29%) sys  22.22
( 3%) wall
 reload CSE regs       :   2.22 ( 0%) usr   0.01 ( 0%) sys   2.24
( 0%) wall
 flow 2                :   0.14 ( 0%) usr   0.00 ( 0%) sys   0.13
( 0%) wall
 rename registers      :   0.19 ( 0%) usr   0.00 ( 0%) sys   0.19
( 0%) wall
 machine dep reorg     :   0.16 ( 0%) usr   0.00 ( 0%) sys   0.16
( 0%) wall
 shorten branches      :   0.17 ( 0%) usr   0.00 ( 0%) sys   0.18
( 0%) wall
 final                 :   0.22 ( 0%) usr   0.01 ( 0%) sys   0.23
( 0%) wall
 rest of compilation   :   3.31 ( 1%) usr   0.00 ( 0%) sys   3.29
( 0%) wall
 TOTAL                 : 597.73             4.40           672.00

The stage combiner seems to take a lot of compile time.. What exactly
happens in 'combining' and can I do something to reduce it?

Akanksha