Profiling on S390

[Richard Henderson]

On Wed, Apr 23, 2003 at 08:50:15PM +0200, Jan Hubicka wrote:
> Perhaps, but Zdenek already has come code to measure extra stuff (like
> value ranges) that do other thinks than plain add.  How would one
> accomplish that?

Hum.  Perhaps

  (1) Do life analysis to verify something's live across here.  Here we
      only have to check hard registers, and then we only have to care
      about those with

	GET_MODE_CLASS (reg_raw_mode[i]) == MODE_CC.

      In the vast majority of cases, no such will be live, so we can
      avoid extra work.

  (2) Generate the code sequence for the edge.  Examine it to see if
      the flags register is actually killed.  If not, do nothing.
      Should help Sparc-like targets that have fine-grained control
      over the setting of the flags register.

  (3) Locate the (a) set that causes the flags register(s) to be live.
      Remember the mode of the register, and we'll use gen_move_insn to
      save/restore the value to a pseudo.  If AVOID_CCMODE_COPIES, abort;
      either the machine description or an optimizer is incorrect.

      There are probably targets for which either AVOID_CCMODE_COPIES
      or CCmode move support is missing.

      Document that AVOID_CCMODE_COPIES implies that the flags register
      cannot be live across basic blocks.


r~