re PR debug/77844 (Compilation of simple C++ example exhaust memory)
PR debug/77844
* valtrack.c: Include rtl-iter.h.
(struct rtx_subst_pair): Add insn field.
(propagate_for_debug_subst): If pair->to contains at least 2
regs, create a DEBUG_INSN with a debug temp before pair->insn
and replace from with the debug temp instead of pair->to.
(propagate_for_debug): Initialize p.insn.
* combine.c (insn_uid_check): New inline function.
(INSN_COST, LOG_LINKS): Use it instead of INSN_UID.
(find_single_use, combine_instructions,
cant_combine_insn_p, try_combine): Use NONDEBUG_INSN_P instead of
INSN_P.
* g++.dg/opt/pr77844.C: New test.
From-SVN: r243662