Re: [build] Restore arm-eabi bootstrap (PR target/50978)

[Paolo Bonzini <bonzini at gnu dot org>]

Ok, so let's do the analysis.  Looks like there are problems in t-rtems 
and sh/t-sh, in addition to ARM.  But I think all of them can be changed.

> > ./config/mcore/t-mcore:HOST_LIBGCC2_CFLAGS = -O3 -DNO_FLOATLIB_FIXUNSDFSI #-msifilter

Used as

        tmake_file="mcore/t-mcore t-fdpbit"

would not be a problem to change to +=

> > ./config/m32r/t-m32r:HOST_LIBGCC2_CFLAGS = -G 0

Same:

        tmake_file="m32r/t-m32r t-fdpbit"

> > ./config/t-rtems:HOST_LIBGCC2_CFLAGS = -I$(srcdir)/../newlib/libc/sys/rtems/include

This was LIBGCC2_INCLUDES before your patches.

You're also missing it in many cases: arm, avr, bfin, moxie, h8300, 
lm32, m32r, m68k, mips, powerpc, sh, m32c.

> > ./config/avr/t-avr:HOST_LIBGCC2_CFLAGS = -DDF=SF -Dinhibit_libc -mcall-prologues -Os

avr-*-rtems*)
        tmake_file="$tmake_file avr/t-avr t-fpbit"
        tm_file="$tm_file avr/avr-lib.h"
        # Don't use default.
        extra_parts=
        ;;

tmake_file seems to be empty at this point, but let's change it to +=

> > ./config/h8300/t-h8300:HOST_LIBGCC2_CFLAGS = -DDF=SF

Same, safe to change.

> > ./config/lm32/t-elf:HOST_LIBGCC2_CFLAGS = -G 0 -msign-extend-enabled

lm32-*-elf*|lm32-*-rtems*)
        extra_parts="$extra_parts crti.o crtn.o"
        tmake_file="lm32/t-lm32 lm32/t-elf t-softfp-sfdf t-softfp"
        ;;

Safe to change.

> > ./config/mmix/t-mmix:HOST_LIBGCC2_CFLAGS = -mlibfuncs -O2

mmix-knuth-mmixware)
        extra_parts="crti.o crtn.o crtbegin.o crtend.o"
        tmake_file="${tmake_file} ${cpu_type}/t-${cpu_type}"
        ;;

Safe to change.

> > ./config/mips/t-elf:HOST_LIBGCC2_CFLAGS = -G 0

Only comes after mips/t-mips, safe to change.

> > ./config/picochip/t-picochip:HOST_LIBGCC2_CFLAGS = -DDF=SF -I../../includes/

picochip-*-*)
        tmake_file="picochip/t-picochip t-fpbit"
        ;;

Safe to change.

> > ./config/sh/t-sh:HOST_LIBGCC2_CFLAGS = -mieee

Wrong, sh/t-sh comes after t-libgcc-pic for sh*-*-linux*
.
> > ./config/c6x/t-elf:HOST_LIBGCC2_CFLAGS = -msdata=none

Safe to change.

> > ./config/t-openbsd-thread:HOST_LIBGCC2_CFLAGS=-pthread

Wrong, overrides t-libgcc-pic.

> > ./config/bfin/t-elf:HOST_LIBGCC2_CFLAGS = $(PICFLAG)

Safe to change.  Can be removed altogether and replaced with t-libgcc-pic.

> > ./config/stormy16/t-stormy16:HOST_LIBGCC2_CFLAGS = -O2

Seems unused to me, because this is not true anymore:

 tmake_file
       A list of machine-description-specific makefile-fragments,
       if different from "$cpu_type/t-$cpu_type".
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

> > ./config/t-vxworks:HOST_LIBGCC2_CFLAGS =

Can be zapped.  But LIBGCC2_DEBUG_CFLAGS cannot, the default is "-g"

> > ./config/arm/t-strongarm-elf:HOST_LIBGCC2_CFLAGS = -fno-inline

Wrong, as you found it should be changed to += because it comes after 
t-libgcc-pic for arm*-*-freebsd*.

> > ./config/arm/t-elf:HOST_LIBGCC2_CFLAGS = -fno-inline

Wrong, topic of this thread.

> > ./config/pdp11/t-pdp11:HOST_LIBGCC2_CFLAGS = -O2 -mfloat32

Safe to change.

Overall I suggest:

* change t-rtems back to LIBGCC2_INCLUDES and add it for the missing 
targets;

* change all to += except when a better course of action is suggested above.

Of course unless you disagree with the analysis or had a reason for the 
t-rtems changes. :)  Let's commit the two as separate patches.

Paolo