re PR rtl-optimization/15139 (cc1 uses excessive amounts of memory compiling small...

re PR rtl-optimization/15139 (cc1 uses excessive amounts of memory compiling small routine)

	PR rtl-optimization/15139
	* combine.c: Include params.h.
	(count_rtxs): New function.
	(record_value_for_reg): If replace_rtx would replace at least
	2 occurrences of REG in VALUE and TEM is really large, replace REG with
	(clobber (const_int 0)) instead of TEM.
	* params.def (PARAM_MAX_LAST_VALUE_RTL): New.
	* params.h (MAX_LAST_VALUE_RTL): New.
	* Makefile.in (combine.o): Depend on $(PARAMS_H).
	* doc/invoke.texi (--param max-last-value-rtl=N): Document.

	* gcc.dg/20050111-2.c: New test.

From-SVN: r93892