gcc optimization flag breakdown

[Andrew Haley]

Nathan Thomas writes:
 > Hi all,
 > 
 > ===> gcc 4.1.1 (release), AIX 5.3
 > 
 > What else does the -O1 flag turn on besides the options listed in the following 
 > document?  Is there any way to turn these on/off incrementally?
 > 
 > http://gcc.gnu.org/onlinedocs/gcc-4.1.1/gcc/Optimize-Options.html#Optimize-Options
 > 
 > I'm trying to isolate the cause of excessively long compile times for a c++ code 
 > when both debug information (-g) and any optimization level (O1/O2/O3) are enabled.
 > 
 > The compile time is fine when I explicitly pass all the flags that -O1 is 
 > documented to engage along with -g.  However, it blows up (in the assembler, up 
 > to 10x) when I call -O1 directly.

Unless you use -O, you get no optimization.  Turning the indivisual
flags on does nothing.

Andrew.