[PATCH] PPC64 Poor assembly coding style

[Linas Vepstas]

Hi,

Doug Maxey reported a bug with the latest/greatest gas assembler
that demonstrates some poor coding style in entry.S and head.S.
The following patch cleans up that style, and also avoids assembler
confusion.  Basically, in entry.S,

 cmpldi  0,r0,NR_syscalls   should be written as either

 cmpldi  r0,NR_syscalls   or as    cmpldi  cr0,r0,NR_syscalls

All three forms are theoretically equivalent; in practice,
I find the first alternative the cleanest (and also consistent
with usage elsewhere in the files).

The new assembler seems to be mistaking NR_syscalls for a register
number, which is clearly out of bounds (its not in 0..31).
I think it would be cleaner overall to just drop the superfluous
leading cr0.  There are two other confusing usages, in head.S:
I propose that
  cmpldi  cr0,r5,0 should be cmpldi  r5,0
  cmpld   0,r6,r5  should be cmpld   r6,r5

--linas

Signed-off-by: Linas Vepstas <linas at linas.org>

-------------- next part --------------


Hi,

Doug Maxey reported a bug with the latest/greatest gas assembler
that demonstrates some poor coding style in entry.S and head.S.
The following patch cleans up that style, and also avoids assembler 
confusion.  Basically, in entry.S,

 cmpldi  0,r0,NR_syscalls   should be written as either

 cmpldi  r0,NR_syscalls   or as    cmpldi  cr0,r0,NR_syscalls

All three forms are theoretically equivalent; in practice,
I find the first alternative the cleanest (and also consistent
with usage elsewhere in the files).

The new assembler seems to be mistaking NR_syscalls for a register
number, which is clearly out of bounds (its not in 0..31).
I think it would be cleaner overall to just drop the superfluous
leading cr0.  There are two other confusing usages, in head.S:
I propose that 
  cmpldi  cr0,r5,0 should be cmpldi  r5,0
  cmpld   0,r6,r5  should be cmpld   r6,r5

--linas

Signed-off-by: Linas Vepstas <linas at linas.org>


===== arch/ppc64/kernel/entry.S 1.46 vs edited =====
--- 1.46/arch/ppc64/kernel/entry.S	2004-10-07 16:52:16 -05:00
+++ edited/arch/ppc64/kernel/entry.S	2004-11-08 11:45:59 -06:00
@@ -122,7 +122,7 @@ SystemCall_common:
 	andi.	r11,r10,_TIF_SYSCALL_T_OR_A
 	bne-	syscall_dotrace
 syscall_dotrace_cont:
-	cmpldi	0,r0,NR_syscalls
+	cmpldi	r0,NR_syscalls
 	bge-	syscall_enosys
 
 system_call:			/* label this so stack traces look sane */
===== arch/ppc64/kernel/head.S 1.81 vs edited =====
--- 1.81/arch/ppc64/kernel/head.S	2004-10-19 02:18:43 -05:00
+++ edited/arch/ppc64/kernel/head.S	2004-11-08 11:49:04 -06:00
@@ -1303,7 +1303,7 @@ _GLOBAL(__start_initialization_multiplat
 	/*
 	 * Are we booted from a PROM Of-type client-interface ?
 	 */
-	cmpldi	cr0,r5,0
+	cmpldi	r5,0
 	bne	.__boot_from_prom		/* yes -> prom */
 
 	/* Save parameters */
@@ -1439,7 +1439,7 @@ _GLOBAL(copy_and_flush)
 	dcbst	r6,r3			/* write it to memory		*/
 	sync
 	icbi	r6,r3			/* flush the icache line	*/
-	cmpld	0,r6,r5
+	cmpld	r6,r5
 	blt	4b
 	sync
 	addi	r5,r5,8