Fix internal compiler error on "var2 = var1 + 1" patterns This appears to be the correct fix. It was provided by Tormod Volden (debian.tormod@gmail.com). The final commit is substantially different from Tormod's submission mostly due to housecleaning (removing the old patches and updating the README). Tormod's comments follow. The original addhi_mem_1 "insn" instruction pattern /matches/ two memory operands, just with the /constraint/ that these are the same location. A pattern match tells the compiler "you should be able to use this, but you might have to work on it to meet the constraints". For typical constraints on registers the compiler can add "reloads", moving stuff between registers or from memory, until the constraints are met and the instruction can be used. However, in this case, no amount of reloads can make two memory locations the same if they already weren't, so the compiler breaks down and cries "unable to generate reloads". It seems this issue only appears if optimization is enabled. The proof is in gcc's reload.c and is left as an exercise to the reader. Limiting the matching pattern to identical memory operands avoids these situations, while allowing the common "var++" cases. References: The pattern/constraints difference is explained in https://gcc.gnu.org/onlinedocs/gccint/Simple-Constraints.html#index-other-register-constraints-3335

/*
lw_stack.h

Copyright © 2010 William Astle

This file is part of LWTOOLS.

LWTOOLS is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.

You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef ___lw_stack_h_seen___
#define ___lw_stack_h_seen___


#ifdef ___lw_stack_c_seen___
struct lw_stack_node_priv
{
	void *data;
	struct lw_stack_node_priv *next;
};

struct lw_stack_priv
{
	struct lw_stack_node_priv *head;
	void (*freefn)(void *d);
};

typedef struct lw_stack_priv * lw_stack_t;


#else /* def ___lw_stack_c_seen___ */

typedef void * lw_stack_t;
lw_stack_t lw_stack_create(void (*freefn)(void *d));
void lw_stack_destroy(lw_stack_t S);
void *lw_stack_top(lw_stack_t S);
void *lw_stack_pop(lw_stack_t S);
void lw_stack_push(lw_stack_t S, void *item);

#endif /* def ___lw_stack_c_seen___ */

#endif /* ___lw_stack_h_seen___ */