Re: `$' in identifiers -vs- PPC Linux

[Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>]

On Tue, 17 Oct 2000, Geoff Keating wrote:
> > From: Franz Sirl <Franz.Sirl-kernel@lauterbach.com>
> > Date: Tue, 17 Oct 2000 21:37:53 +0200
> > Cc: gcc-patches@gcc.gnu.org
> >
> > Well, tell me what do you want to have out of rs6000.h and I'll do
> > the boring work :-). I just couldn't draw a sensible line for all
> > the alignment, type and ASM macros myself.
>
> I think that when the ppc-elf64 stuff comes in all this will need to
> be rearranged anyway, because suddenly we'll have aix-xcoff and
> aix-elf64 and powerpc-elf64.  So there's no need to tinker with it now.

OK :)

> > > > > make no real sense to move into aix.h IMHO.
> > > > >
> > > > > The patch also syncs the ASM_APP_* macros for Linux on PPC and
> > > > > fixes the CONSTRUCTOR handling in rs6000.c. Geoff, related to the
> > > > > CONSTRUCTOR handling I also want to revive execute/20000516-1.c
> > > > > from CVS, this test is meant to pass and is _different_ from
> > > > > execute/20000722-1.c. The test verifies that CONSTRUCTOR data is
> > > > > put into a writeable section. I didn't notice yet that you did
> > > > > remove it, but the removal was wrong.
> > >
> > > The testcase was failing sometimes, and passing sometimes, based I
> > > believe on segment sizes or something, which was annoying.
> > >
> > > The data does not need to be put in a writable section.  It has to be
> > > copied from wherever it is into a local temporary.
> > >
> > > For instance,
> > >
> > > struct s
> > > {
> > >   int value;
> > >   char *string;
> > > };
> > >
> > > int i;
> > > for (i = 0; i < 4; i++)
> > > {
> > >    struct s *t = & (struct s) { 3, "hey there" };
> > >    if (t->value != 3)
> > >      abort();
> > >    t->value = 4;
> > >    if (t->value != 4)
> > >      abort();
> > > }
> >
> > I don't quite understand? This code fails without my patch and passes
> > with it?
>
> No, this code fails on every gcc release to date I believe.  Certainly
> it fails on x86 and ppc with current gcc versions.  But C99 says it
> should pass.
>
> > Note that my patch (or something similar) fixes Linux kernel compilation,
> > without it you can't put a kernel image into ROM, cause it tries to write
> > to it. This is a showstopper for the embedded people. Additionally the
> > same functionality is available on x86, which passed the testcase too.
>
> Your patch fixes this specific problem, but the underlying bug is
> still there, and if the underlying bug was fixed your patch would
> probably be unnecessary.  Your patch is OK for a branch, but not for
> the mainline.
>
> > On what platforms did the test FAIL?
>
> I had to take your test out because it would fail or pass depending on
> the size of crt0, which was confusing the automated tester.  The new
> testcase shows the same underlying problem (that we aren't using
> temporaries) and fails every time.
>
> > I would rather think these need fixes too, that's why the testcase
> > was added in the first place, it tests if the functionality (I think
> > this is a GCC extension) is correctly implemented.
>
> It's now in the ISO C standard, as section 6.5.2.5, with
> better-defined semantics.  The bit that would need changing is
> cast_expr in c-parse.in.

Aaahhh! So you meant to say there _is_ a bug, but it has to be fixed in a 
different way. Fine with me.

Here is the updated patch, OK to commit?

BTW, can you approve this PPC related fix too? It's in my sources for nearly 
a year now and awaits approval :-):
http://gcc.gnu.org/ml/gcc-patches/1999-11n/msg00616.html

Some related discussion can be found here:
http://gcc.gnu.org/ml/gcc-patches/1999-11n/msg00268.html

Franz.

        * rs6000/rs6000.h (NO_DOLLAR_IN_LABEL, DOLLARS_IN_IDENTIFIERS,
        ENCODE_SECTION_INFO, ASM_OUTPUT_SPECIAL_POOL_ENTRY_P): Move from
        here...
        * rs6000/aix.h: ...to here.
        * rs6000/linux.h (ASM_APP_ON, ASM_APP_OFF): Define to Linux-style.
Index: aix.h
===================================================================
RCS file: /cvs/gcc/egcs/gcc/config/rs6000/aix.h,v
retrieving revision 1.7
diff -u -p -r1.7 aix.h
--- aix.h	2000/08/22 19:27:31	1.7
+++ aix.h	2000/08/31 19:30:42
@@ -50,6 +50,17 @@ Boston, MA 02111-1307, USA.  */
 
 #define FASCIST_ASSEMBLER
 
+/* We define this to prevent the name mangler from putting dollar signs into
+   function names.  */
+
+#define NO_DOLLAR_IN_LABEL
+
+/* We define this to 0 so that gcc will never accept a dollar sign in a
+   variable name.  This is needed because the AIX assembler will not accept
+   dollar signs.  */
+
+#define DOLLARS_IN_IDENTIFIERS 0
+
 /* AIX does not have any init/fini or ctor/dtor sections, so create
     static constructors and destructors as normal functions.  */
 /* #define ASM_OUTPUT_CONSTRUCTOR(file, name) */
@@ -227,6 +238,30 @@ toc_section ()						\
     }							\
 }
 
+/* Return non-zero if this entry is to be written into the constant
+   pool in a special way.  We do so if this is a SYMBOL_REF, LABEL_REF
+   or a CONST containing one of them.  If -mfp-in-toc (the default),
+   we also do this for floating-point constants.  We actually can only
+   do this if the FP formats of the target and host machines are the
+   same, but we can't check that since not every file that uses
+   GO_IF_LEGITIMATE_ADDRESS_P includes real.h.  We also do this when
+   we can write the entry into the TOC and the entry is not larger
+   than a TOC entry.  */
+
+#define ASM_OUTPUT_SPECIAL_POOL_ENTRY_P(X, MODE)			\
+  (TARGET_TOC								\
+   && (GET_CODE (X) == SYMBOL_REF					\
+       || (GET_CODE (X) == CONST && GET_CODE (XEXP (X, 0)) == PLUS	\
+	   && GET_CODE (XEXP (XEXP (X, 0), 0)) == SYMBOL_REF)		\
+       || GET_CODE (X) == LABEL_REF					\
+       || (GET_CODE (X) == CONST_INT 					\
+	   && GET_MODE_BITSIZE (MODE) <= GET_MODE_BITSIZE (Pmode))	\
+       || (GET_CODE (X) == CONST_DOUBLE					\
+	   && (TARGET_POWERPC64						\
+	       || TARGET_MINIMAL_TOC					\
+	       || (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT		\
+		   && ! TARGET_NO_FP_IN_TOC)))))
+
 /* Select section for constant in constant pool.
 
    On RS/6000, all constants are in the private read-only data area.
@@ -239,6 +274,17 @@ toc_section ()						\
   else							\
     read_only_private_data_section ();			\
 }
+
+/* If we are referencing a function that is static or is known to be
+   in this file, make the SYMBOL_REF special.  We can use this to indicate
+   that we can branch to this function without emitting a no-op after the
+   call.  Do not set this flag if the function is weakly defined. */
+
+#define ENCODE_SECTION_INFO(DECL)			\
+  if (TREE_CODE (DECL) == FUNCTION_DECL			\
+      && (TREE_ASM_WRITTEN (DECL) || ! TREE_PUBLIC (DECL)) \
+      && ! DECL_WEAK (DECL))				\
+    SYMBOL_REF_FLAG (XEXP (DECL_RTL (DECL), 0)) = 1;
 
 /* Indicate that jump tables go in the text section.  */
 
Index: linux.h
===================================================================
RCS file: /cvs/gcc/egcs/gcc/config/rs6000/linux.h,v
retrieving revision 1.19
diff -u -p -r1.19 linux.h
--- linux.h	2000/04/14 23:16:25	1.19
+++ linux.h	2000/08/31 19:30:42
@@ -54,6 +54,14 @@ Boston, MA 02111-1307, USA.  */
 #undef TARGET_VERSION
 #define TARGET_VERSION fprintf (stderr, " (PowerPC GNU/Linux)");
 
+/* Override rs6000.h definition.  */
+#undef ASM_APP_ON
+#define ASM_APP_ON "#APP\n"
+
+/* Override rs6000.h definition.  */
+#undef ASM_APP_OFF
+#define ASM_APP_OFF "#NO_APP\n"
+
 #undef DEFAULT_VTABLE_THUNKS
 #ifndef USE_GNULIBC_1
 #define DEFAULT_VTABLE_THUNKS 1
Index: rs6000.h
===================================================================
RCS file: /cvs/gcc/egcs/gcc/config/rs6000/rs6000.h,v
retrieving revision 1.90
diff -u -p -r1.90 rs6000.h
--- rs6000.h	2000/08/14 05:59:50	1.90
+++ rs6000.h	2000/08/31 19:30:55
@@ -2327,17 +2327,6 @@ extern int rs6000_trunc_used;
    the end of the line.  */
 #define ASM_COMMENT_START " #"
 
-/* We define this to prevent the name mangler from putting dollar signs into
-   function names.  */
-
-#define NO_DOLLAR_IN_LABEL
-
-/* We define this to 0 so that gcc will never accept a dollar sign in a
-   variable name.  This is needed because the AIX assembler will not accept
-   dollar signs.  */
-
-#define DOLLARS_IN_IDENTIFIERS 0
-
 /* Implicit library calls should use memcpy, not bcopy, etc.  */
 
 #define TARGET_MEM_FUNCTIONS
@@ -2348,43 +2337,8 @@ extern int rs6000_trunc_used;
 
 #define EXCEPTION_SECTION data_section
 
-/* If we are referencing a function that is static or is known to be
-   in this file, make the SYMBOL_REF special.  We can use this to indicate
-   that we can branch to this function without emitting a no-op after the
-   call.  Do not set this flag if the function is weakly defined. */
-
-#define ENCODE_SECTION_INFO(DECL)			\
-  if (TREE_CODE (DECL) == FUNCTION_DECL			\
-      && (TREE_ASM_WRITTEN (DECL) || ! TREE_PUBLIC (DECL)) \
-      && ! DECL_WEAK (DECL))				\
-    SYMBOL_REF_FLAG (XEXP (DECL_RTL (DECL), 0)) = 1;
-
 /* Flag to say the TOC is initialized */
 extern int toc_initialized;
-
-/* Return non-zero if this entry is to be written into the constant
-   pool in a special way.  We do so if this is a SYMBOL_REF, LABEL_REF
-   or a CONST containing one of them.  If -mfp-in-toc (the default),
-   we also do this for floating-point constants.  We actually can only
-   do this if the FP formats of the target and host machines are the
-   same, but we can't check that since not every file that uses
-   GO_IF_LEGITIMATE_ADDRESS_P includes real.h.  We also do this when
-   we can write the entry into the TOC and the entry is not larger
-   than a TOC entry.  */
-
-#define ASM_OUTPUT_SPECIAL_POOL_ENTRY_P(X, MODE)			\
-  (TARGET_TOC								\
-   && (GET_CODE (X) == SYMBOL_REF					\
-       || (GET_CODE (X) == CONST && GET_CODE (XEXP (X, 0)) == PLUS	\
-	   && GET_CODE (XEXP (XEXP (X, 0), 0)) == SYMBOL_REF)		\
-       || GET_CODE (X) == LABEL_REF					\
-       || (GET_CODE (X) == CONST_INT 					\
-	   && GET_MODE_BITSIZE (MODE) <= GET_MODE_BITSIZE (Pmode))	\
-       || (GET_CODE (X) == CONST_DOUBLE					\
-	   && (TARGET_POWERPC64						\
-	       || TARGET_MINIMAL_TOC					\
-	       || (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT		\
-		   && ! TARGET_NO_FP_IN_TOC)))))
 
 /* Macro to output a special constant pool entry.  Go to WIN if we output
    it.  Otherwise, it is written the usual way.