[patch] Banish RTL from the front ends

[Steven Bosscher <stevenb dot gcc at gmail dot com>]

Hi,

After this patch, no front end will ever include rtl.h and still build.

Well, almost anyway. There are three files that still need to include
rtl.h, but I would like to work on those after first making sure
nothing new can show up ever again. The c-common.c bit is easy, the
java bit is a bit more difficult, and I sent out an RFH for the ada
bits yesterday because I have no idea what to do there.

I have looked through the target specific code, and I think I've got
everything covered there also, but should something break anyway, let
me know and I'll fix it ASAP.

The Makefile bits have been approved already
(http://gcc.gnu.org/ml/gcc/2010-05/msg00609.html), and so has the
system.h changeto system.h
(http://gcc.gnu.org/ml/gcc/2010-05/msg00596.html)

So I still need the OK from the front end folks.

Bootstrapped (all languages) on x86_64-unknown-linux-gnu.
OK for trunk?

Ciao!
Steven




gcc/ChangeLog:
        * Makefile.in (ALL_CFLAGS): Add file-specific CFLAGS.
        (ALL_HOST_FRONTEND_OBJS): New, for all front-end specific objects.
        (ALL_HOST_BACKEND_OBJS): New, for all backend and target objects.
        (ALL_HOST_OBJS): Now a union of the above two.
        <section "Language makefile fragments">: Add -DIN_GCC_FRONTEND for
        all files in ALL_HOST_FRONTEND_OBJS.
        * system.h: Poison GCC_RTL_H if IN_GCC_FRONTEND is defined.
        * c-common.c: Pretend to be a backend file by undefining
        IN_GCC_FRONTEND (still need rtl.h here).

java/ChangeLog:
        * buildings.c: Pretend to be a backend file by undefining
        IN_GCC_FRONTEND (still need rtl.h here).

ada/ChangeLog:
        * gcc-interface/decl.c: Pretend to be a backend file by undefining
        IN_GCC_FRONTEND (still need rtl.h here).

Index: Makefile.in
===================================================================
--- Makefile.in (revision 159912)
+++ Makefile.in (working copy)
@@ -974,7 +974,7 @@ INTERNAL_CFLAGS = -DIN_GCC @CROSS@

 # This is the variable actually used when we compile. If you change this,
 # you probably want to update BUILD_CFLAGS in configure.ac
-ALL_CFLAGS = $(T_CFLAGS) \
+ALL_CFLAGS = $(T_CFLAGS) $(CFLAGS-$@) \
   $(CFLAGS) $(INTERNAL_CFLAGS) $(COVERAGE_FLAGS) $(WARN_CFLAGS) @DEFS@

 # The C++ version.
@@ -1445,15 +1445,19 @@ OBJS = $(OBJS-common) $(OBJS-md) $(OBJS-

 OBJS-onestep = libbackend.o $(OBJS-archive)

-# This lists all host object files, whether they are included in this
-# compilation or not.
-ALL_HOST_OBJS = $(GCC_OBJS) $(C_OBJS) $(OBJS) libbackend.o \
+# This lists all host objects for the front ends.
+ALL_HOST_FRONTEND_OBJS = $(C_OBJS) \
+  $(foreach v,$(CONFIG_LANGUAGES),$($(v)_OBJS))
+
+ALL_HOST_BACKEND_OBJS = $(GCC_OBJS) $(OBJS) libbackend.o \
   @TREEBROWSER@ main.o gccspec.o version.o intl.o prefix.o cppspec.o \
-  $(foreach v,$(CONFIG_LANGUAGES),$($(v)_OBJS)) \
-  $(COLLECT2_OBJS) $(EXTRA_GCC_OBJS) \
-  mips-tfile.o mips-tdump.o \
+  $(COLLECT2_OBJS) $(EXTRA_GCC_OBJS) mips-tfile.o mips-tdump.o \
   $(GCOV_OBJS) $(GCOV_DUMP_OBJS)

+# This lists all host object files, whether they are included in this
+# compilation or not.
+ALL_HOST_OBJS = $(ALL_HOST_FRONTEND_OBJS) $(ALL_HOST_BACKEND_OBJS)
+
 BACKEND = main.o @TREEBROWSER@ libbackend.a $(CPPLIB) $(LIBDECNUMBER)

 MOSTLYCLEANFILES = insn-flags.h insn-config.h insn-codes.h \
@@ -1571,6 +1575,13 @@ s-alltree: Makefile
        $(SHELL) $(srcdir)/../move-if-change tmp-all-tree.def all-tree.def
        $(STAMP) s-alltree

+# Now that LANG_MAKEFRAGS are included, we can add special flags to the
+# objects that belong to the front ends.  We add an extra define that
+# causes back-end specific include files to be poisoned, in the hope that
+# we can avoid introducing dependencies of the front ends on things that
+# no front end should ever look at (e.g. everything RTL related).
+$(foreach file,$(ALL_HOST_FRONTEND_OBJS),$(eval CFLAGS-$(file) +=
-DIN_GCC_FRONTEND))
+
 #


 # -----------------------------
Index: system.h
===================================================================
--- system.h    (revision 159912)
+++ system.h    (working copy)
@@ -789,6 +789,12 @@ extern void fancy_abort (const char *, i
   VA_FIXEDARG VA_CLOSE VA_START
 #endif /* IN_GCC */

+/* Front ends should never have to include middle-end headers.  Enforce
+   this by poisoning the header double-include protection defines.  */
+#ifdef IN_GCC_FRONTEND
+#pragma GCC poison GCC_RTL_H
+#endif
+
 /* Note: not all uses of the `index' token (e.g. variable names and
    structure members) have been eliminated.  */
 #undef bcopy
Index: c-common.c
===================================================================
--- c-common.c  (revision 159912)
+++ c-common.c  (working copy)
@@ -19,6 +19,10 @@ You should have received a copy of the G
 along with GCC; see the file COPYING3.  If not see
 <http://www.gnu.org/licenses/>.  */

+/* FIXME: Still need to include rtl.h here (via expr.h) in a front-end file.
+   Pretend this is a back-end file.  */
+#undef IN_GCC_FRONTEND
+
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"
@@ -47,9 +51,6 @@ along with GCC; see the file COPYING3.
 #include "target-def.h"
 #include "libfuncs.h"

-/* FIXME: Still need to include rtl.h here (via expr.h) in a front-end file.
-   Pretend this is a back-end file.  */
-#define IN_GCC_BACKEND
 #include "expr.h" /* For vector_mode_valid_p */

 /* FIXME: Needed for TARGET_ENUM_VA_LIST, which should be a target hook.  */
Index: java/builtins.c
===================================================================
--- java/builtins.c     (revision 159912)
+++ java/builtins.c     (working copy)
@@ -24,6 +24,9 @@ The Free Software Foundation is independ

 /* Written by Tom Tromey <tromey@redhat.com>.  */

+/* FIXME: Still need to include rtl.h here (see below).  */
+#undef IN_GCC_FRONTEND
+
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"
Index: ada/gcc-interface/decl.c
===================================================================
--- ada/gcc-interface/decl.c    (revision 159912)
+++ ada/gcc-interface/decl.c    (working copy)
@@ -23,6 +23,10 @@
  *                                                                          *
  ****************************************************************************/

+/* FIXME: Still need to include rtl.h here (via expr.h) because this file
+   actually generates RTL (search for gen_rtx_* in gnat_to_gnu_entity).  */
+#undef IN_GCC_FRONTEND
+
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"