* genrecog.c (write_tree): Output code to clear insn_extract cache.
* genattrtab.c (write_attr_case): Gen call to extract_insn_cache
instead of extract_insn and extract_constrain_insn_cache instead of
extract_insn and constrain_operands.
* recog.c (extract_insn_cached, extract_constrain_insn_cached):
New functions.
(extract_insn): Clear which_alternative.
(constrain_operands): Set which_alternative to -1 when failed.
* recog.h (extract_constrain_insn_cached, extract_insn_cached):
Declare.