Re: bal instruction in gcc 3.x

[Pete Popov <ppopov@embeddedalley.com>]

[-- Attachment #1: Type: text/plain, Size: 2088 bytes --]


Try the attached patch instead.

Pete

On Tue, 2005-07-19 at 22:49 +0530, Kishore K wrote:
> On 7/19/05, Ralf Baechle <ralf@linux-mips.org> wrote:
> > On Tue, Jul 19, 2005 at 10:00:20PM +0530, Kishore K wrote:
> > 
> > > We are facing a problem when U-boot is compiled with gcc 3.x
> > >
> > > U-boot  uses the following instruction in one of the files.
> > >
> > > bal jump_to_symbol
> > >
> > > This code gets compiled without any problem with gcc2. However, if I
> > > compile the code
> > > with gcc3, it exits with the error "Cannot branch to unknown symbol".
> > >
> > > What should we do to circumvent this problem ?
> > >
> > > I replaced
> > >
> > > bal jump_to_symbol
> > >
> > > by
> > >
> > > la t9, jump_to_symbol
> > > jalr t9
> > >
> > > Then code gets compiled properly without any problem. Please let me
> > > know, whether this
> > > is correct way of fixing the problem. I am newbie to MIPS assembly
> > > language. Why this
> > > change is required with gcc 3.x compiler ?
> > 
> > FIrst of all, gcc doesn't care at all about your assembler code, that's
> > the assembler which you must have changed along with that.
> > 
> > There used to be no relocation type to represent a branch to an external
> > symbol in an ELF file which is why gas is throwing an error message, so
> > gas is throwing an error message.  Latest gas fixed that shortcoming.
> > I think there was a bug in somewhat older gas which resulted in such
> > invalid code actually being accepted even though it shouldn't have been.
> > 
> >   Ralf
> 
> Thank you very much for the reply.
> 
> First of all code got compiled only after removing the option
> -mips-allow-branch-to-undefined from Makefile. If this option is
> included, compilation fails saying that option is invalid. I am using
> binutils-2.14.90.06.
> Same problem is observed even with binutils 2.15.94.0.2.2. 
> 
> Do you mean to say that no change is required in the code snippet 
> 
> bal jump_to_symbol
> 
> and code should get compiled with the latest assembler without any
> problem. Please clearify.
> 
> TIA,
> --kishore
> 

[-- Attachment #2: mips_jalr.diff --]
[-- Type: text/x-patch, Size: 1052 bytes --]

--- start.S	2004-02-06 17:27:17.000000000 -0800
+++ start.S~jalr	2005-01-29 16:13:18.000000000 -0800
@@ -234,21 +234,35 @@
 	li	t0, CONF_CM_UNCACHED
 	mtc0	t0, CP0_CONFIG
 
+	/* Initialize GOT pointer.
+	 */
+	bal	1f
+	nop
+	.word	_GLOBAL_OFFSET_TABLE_ - 1f + 4
+1:
+	move	gp, ra
+	lw	t1, 0(ra)
+	add	gp, t1
+
+
 #ifdef CONFIG_INCA_IP
 	/* Disable INCA-IP Watchdog.
 	 */
-	bal	disable_incaip_wdt
+	la	t9, disable_incaip_wdt
+	jalr	t9
 	nop
 #endif
 
 	/* Initialize any external memory.
 	 */
-	bal	memsetup
+	la	t9, memsetup
+	jalr	t9
 	nop
 
 	/* Initialize caches...
 	 */
-	bal	mips_cache_reset
+	la	t9, mips_cache_reset
+	jalr	t9
 	nop
 
 	/* ... and enable them.
@@ -260,21 +274,13 @@
 	/* Set up temporary stack.
 	 */
 	li	a0, CFG_INIT_SP_OFFSET
-	bal	mips_cache_lock
+	la	t9, mips_cache_lock
+	jalr	t9
 	nop
 
 	li	t0, CFG_SDRAM_BASE + CFG_INIT_SP_OFFSET
 	la	sp, 0(t0)
 
-	/* Initialize GOT pointer.
-	 */
-	bal	1f
-	nop
-	.word	_GLOBAL_OFFSET_TABLE_ - 1f + 4
-1:
-	move	gp, ra
-	lw	t1, 0(ra)
-	add	gp, t1
 	la	t9, board_init_f
 	j	t9
 	nop