commits to ignore:
- remove VMS stuff (not related to compiling)
- misc cleanup (seems like a lot of debug removal)
- remove g++ test cases (g++ doesn't exist anymore in agbcc)
- remove static constuctors/destructors (some decorator)
- remove more objc stuff (unrelated to C compilation)
- remove live ranges (seems like non-default compiler flag, not documented in gcc 2.95.3 docs)
- remove standalone preprocessor (cpp provided with modern gcc for compiling agbcc)
- clean up limits.h (related to max value of something (e.g. maxint), doesn't seem related to compiling)
- clean up standard headers (unrelated to arm compilation)
- remove use of strings.h (refactoring via replacement of strings.h functions with library functions)
- rely on configure less (refactoring some printing stuff which is probably tied to configure)
- remove alternate versions of thumb files (!! check this out later)
- clean up thumb code (!! check this out later)
- clean up thumb.c more (!! check this out later, mostly looks like formatting fixes but thumb_exit was modified)
- remove unneeded function (small commit, only removes some clearly unused code)
- fix md (main change seems to be https://github.com/pret/agbcc/commit/ee6378488b6ef2654dcbffaaf1319c415c552f27#diff-1cff883ac32be6938d71c9a7da05004fL1101 , everything else looks like exit code replacements)
- remove unused files (seems like they weren't used at all)
- remove unused simple return code (removed code only defined through undefined cpp flags)
- remove delay slot and stack reg code (unused by arm?)
- remove epilogue delay list (! current_function_epilogue_delay_list is actually used in arm.c, look at this later)
- remove PIC (non-working and disabled) (non-working and disabled)
- remove macros for old compilers (removes undefined cpp flags, very small commit)
- remove insn scheduling (not supported with thumb) (!!! supported with arm, need to re-add)
- remove more unused files (removes some c compiler tests)
- remove old version of loop.c (removes old version (loop_[date].c))
- remove some hard reg ifdefs (!!! removed REG_ALLOC_ORDER, and CONDITIONAL_REGISTER_USAGE)
- clean up more reg ifdefs (!!! removed HARD_FRAME_POINTER_REGNUM, PUSH_ROUNDING, hard_frame_pointer_rtx)
- remove exit_ignore_stack ifdefs (!!! removed EXIT_IGNORE_STACK, clear_pending_stack_adjust)
- kill libiberty (only touches gcc stuff irrelevant to arm compilation)
- trim makefile (unrelated to arm compilation)
- remove more files (replace assert.h with <assert.h>, doprint.c, dostage2, dostage3, remove some dwarf debugging stuff)
- get rid of PROTO macros (only removes PROTO macros (I hope))
- remove ANSI_PROTOTYPES ifdefs (ANSI_PROTOTYPES is defined by default)
- get rid of VA_START macro (VA_START -> va_start)
- get rid of PTR macros (NULL_PTR -> NULL, GENERIC_PTR -> void *)
- stop using configure script to generate header files (configure related)
- delete xm-i386.h (build/Makefile related)


* evaluates to true for thumb and arm
- evaluates to false for thumb and arm
unused/ignore flags for arm:
- PCC_STATIC_STRUCT_RETURN
- LEAF_REGISTERS
- DELAY_SLOTS
- STACK_REGS
- ADJUST_INSN_LENGTH
- CASE_VECTOR_SHORTEN_MODE
- NON_SAVING_SETJMP
- LEAF_REG_REMAP
- ASM_OUTPUT_MAX_SKIP_ALIGN
* REAL_ARITHMETIC
- BUFSIZ
- HAVE_return (special user defined flag?)
- HARD_REG_SET (FIRST_PSEUDO_REG starts at 27, 32 bits in unsigned int)
- RELOAD_ALLOC_ORDER
* WORD_REGISTER_OPERATIONS
* ARG_POINTER_REGNUM = 26
* FRAME_POINTER_REGNUM = 25
* FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
- SECONDARY_MEMORY_NEEDED
* ELIMINABLE_REGS
- EPILOGUE_USES
- INSN_REFERENCES_ARE_DELAYED

used keywords:
- INSN_SCHEDULING
- REG_ALLOC_ORDER
- CONDITIONAL_REGISTER_USAGE
- HARD_FRAME_POINTER_REGNUM
- PUSH_ROUNDING
- hard_frame_pointer_rtx
- EXIT_IGNORE_STACK
- clear_pending_stack_adjust


don't need to re-add FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM

thumb:
HARD_FRAME_POINTER_REGNUM = 7
FRAME_POINTER_REGNUM = 7
ARG_POINTER_REGNUM = 16
arm:
HARD_FRAME_POINTER_REGNUM = 11
FRAME_POINTER_REGNUM = 25
ARG_POINTER_REGNUM = 26


attrs in arm.md:
- prog_mode = "prog32"
- is_strongarm = "no"
- fpu = "yes"
- ldsched = "no"
- model_wbuf = "no"
- core?

defined function units:
- fpa

undefined function units:
- write_buf
- write_blockage


used flags:
- INSN_SCHEDULING (for floating point)
-