re PR middle-end/34450 (compile takes up 1.8 GB RAM at -O1)

2007-12-13  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/34450
	* params.def (PARAM_SCCVN_MAX_SCC_SIZE): New param.
	* invoke.texi (sccvn-max-scc-size): Document.
	* Makefile.in (tree-ssa-sccvn.o): Add $(PARAMS_H) dependency.
	* tree-ssa-sccvn.h (run_scc_vn): Return true on success, false
	on error.
	* tree-ssa-sccvn.c (params.h): Include.
	(DFS): Return true if all went well, return false as soon as
	a SCC exceeds the size of PARAM_SCCVN_MAX_SCC_SIZE.
	(run_scc_vn): Return true if all went well, return false if
	we aborted during DFS.
	* tree-ssa-pre.c (execute_pre): Check if SCCVN finished
	successfully, otherwise bail out.

From-SVN: r130895