On Mon, Nov 5, 2012 at 7:58 PM, SANKAR <chnabsankar@xxxxxxxxx> wrote: > > 1. It is observed that for many parameters(almost for 90% ) the max value is > given as '0'. > > How to interepret this? What is the real Maximum value that these parameters > can take? It means that the compiler does not enforce any maximum value when you use --param. The meaning of very large values depends on the parameter. > 2. For some parameters like max-sched-extend-regions-iters, > max-fields-for-field-sensitive etc., the default, min and max value all are > '0' (0,0,0). Then > > what is the necessity to be the parameter, rather it can be the constant. As the documentation says, the real default value for max-fields-for-field-sensitive depends on the optimization level. The parameter has a meaning. As the comment in params.def says, the maximum value is only meaningful if it is larger than the minimum value. In this case the parameter has a minimum value of zero and no maximum. > 3. For parameter 'integer-share-limit' the default value is 251 and the max > and min values are 2,2. Can you explain how to interpret? The minimum is 2 and there is no maximum. > 4. The default value for "max-inline-insns-single" is given as 400 in the > DEFPARAM, whereas the in the comment the default value mentioned as 450. Sounds like a bug. Typically when the code and the comment disagree, you should go with the code. > 5. I hope the values that these parameters can take are discrete numbers > only. Then for some parameters where the possible values are binary, for > example omega-eliminate-redundant-constraints (0,0,1), > use-canonical-types(1,0,1) etc., can they be converted -fno/-f style > options? Sure, they could. Since -f options can take arguments, any --param option could be implemented as a -f option. Generally --param is used for parameters that are only of interest to GCC maintainers. -f options are intended for users. Ian
