Dear Albert ARIBAUD,
In message <4ce0388e.2070...@free.fr> you wrote:
>
> > Register use is documented in the top level README.
>
> My bad: I'd missed that one because I always go straight to the doc/
> directory for documentation of this kind -- the root README I never read
> apart from the first few pages, and I would not have thought it to give
> this level of detail.
;-)
> BTW, a fix to this ./README is in order as GOT is not used any more with
> ELF ARM relocation, so r9 is not needed for this anymore...
Agreed.
> ... and even though I don't like the idea of reserving a register for
> gd, since we must for the moment, then using the (now available) r9
> register would be *more* 'EABI/AAPCS-compliant' than using r8 (as I
> said, one could think of this use of r9 as 'our AAPCS variant').
Actually situation might be differenton ARM. I just did quick and
ditry test for the TX25 board:
diff --git a/arch/arm/cpu/arm926ejs/config.mk b/arch/arm/cpu/arm926ejs/config.mk
index f8ef90f..f8bbeba 100644
--- a/arch/arm/cpu/arm926ejs/config.mk
+++ b/arch/arm/cpu/arm926ejs/config.mk
@@ -21,7 +21,7 @@
# MA 02111-1307 USA
#
-PLATFORM_RELFLAGS += -fno-common -ffixed-r8 -msoft-float
+PLATFORM_RELFLAGS += -fno-common -msoft-float
PLATFORM_CPPFLAGS += -march=armv5te
# =========================================================================
diff --git a/arch/arm/include/asm/global_data.h
b/arch/arm/include/asm/global_data.h
index ada3fbb..7561523 100644
--- a/arch/arm/include/asm/global_data.h
+++ b/arch/arm/include/asm/global_data.h
@@ -86,6 +86,13 @@ typedef struct global_data {
#define GD_FLG_DISABLE_CONSOLE 0x00040 /* Disable console (in & out)
*/
#define GD_FLG_ENV_READY 0x00080 /* Environment imported into hash table
*/
+
+#if 0
#define DECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r8")
+#else /* We could use plain global data, but the resulting code is bigger */
+#define XTRN_DECLARE_GLOBAL_DATA_PTR extern
+#define DECLARE_GLOBAL_DATA_PTR XTRN_DECLARE_GLOBAL_DATA_PTR \
+ gd_t *gd
+#endif
#endif /* __ASM_GBL_DATA_H */
diff --git a/arch/arm/lib/board.c b/arch/arm/lib/board.c
index 1fd5f83..b0de6c7 100644
--- a/arch/arm/lib/board.c
+++ b/arch/arm/lib/board.c
@@ -647,3 +647,14 @@ void hang (void)
puts ("### ERROR ### Please RESET the board ###\n");
for (;;);
}
+
+#if 1 /* We could use plain global data, but the resulting code is bigger */
+/*
+ * Pointer to initial global data area
+ *
+ * Here we initialize it.
+ */
+#undef XTRN_DECLARE_GLOBAL_DATA_PTR
+#define XTRN_DECLARE_GLOBAL_DATA_PTR /* empty = allocate here */
+DECLARE_GLOBAL_DATA_PTR = (gd_t *) (CONFIG_SYS_INIT_SP_ADDR);
+#endif /* 0 */
Compare sizes for "tx25":
text data bss dec hex filename
158730 8668 37120 204518 31ee6 ./u-boot with register
158574 8672 37120 204366 31e4e ./u-boot with global pointer
The global pointer method saves a total of 152 bytes here
(156 in .text saved, but 4 in .data needed).
OK, this is not even 0.1% of the size, but anyway...
Best regards,
Wolfgang Denk
--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de
"Probably the best operating system in the world is the [operating
system] made for the PDP-11 by Bell Laboratories."
- Ted Nelson, October 1977
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