PR optimization/8423
* cse.c (fold_rtx): Only eliminate a CONSTANT_P_RTX to 1 when
its argument is constant, or 0 if !flag_gcse.
* simplify-rtx.c (simplify_rtx): Convert CONSTANT_P_RTX to 1
if it's argument is constant.
* gcse.c (want_to_gcse_p): Ignore CONSTANT_P_RTX nodes.
(hash_scan_set): Don't record CONSTANT_P_RTX expressions.
(do_local_cprop): Don't propagate CONSTANT_P_RTX constants.
* builtins.c (purge_builtin_constant_p): New function to force
instantiation of any remaining CONSTANT_P_RTX nodes.
* rtl.h (purge_builtin_constant_p): Prototype here.
* toplev.c (rest_of_compilation): Invoke purge_builtin_constant_p
pass after GCSE and before loop.
(flag_gcse): No longer static.
* flags.h (flag_gcse): Prototype here.
From-SVN: r61642
