On Thu, Oct 12, 2006 at 02:03:39PM -0400, bile@xxxxxxxxxxxxxx wrote:
> In include/asm-mips/system.h __cmpxchg_u64 is doing
>
> if(cpu_has_llsc) {
> } else if(cpu_has_llsc) {
>
> the first should be (cpu_has_llsc && R10000_LLSC_WAR).
>
> While this probably gets cleaned up during optimization I took
> the liberty of cleaning up the code along with the fix so it's
> not doing the double check and only includes the R10000 workaround
> at compile time.
Please include a Signed-off-by: line when submitting patches.
> diff --git a/include/asm-mips/system.h b/include/asm-mips/system.h
> index dcb4701..bfae6ff 100644
> --- a/include/asm-mips/system.h
> +++ b/include/asm-mips/system.h
> @@ -206,7 +206,7 @@ static inline unsigned long __xchg_u32(v
> {
> __u32 retval;
>
> - if (cpu_has_llsc && R10000_LLSC_WAR) {
> + if (cpu_has_llsc) {
Thanks for spotting this one.
> @@ -216,25 +216,11 @@ static inline unsigned long __xchg_u32(v
> " move %2, %z4 \n"
> " .set mips3 \n"
> " sc %2, %1 \n"
> +#ifdef R10000_LLSC_WAR
This isn't quite right since R10000_LLSC_WAR is defined to 0 if the
workaround is not enabled, so "#if R10000_LLSC_WAR" would be needed
here.
> " beqzl %2, 1b \n"
> -#ifdef CONFIG_SMP
> - " sync \n"
> -#endif
Now the real reason why I don't want to apply your patch is below patch
which is playing fancy tricks with the branch prediction of modern
processors. The R10000 ll/sc workaround _relies_ on the missprediction
of the branch likely branch to work correctly, so this optimization
could not be applied to it that is we need two different versions.
Ralf
commit 23d60625d8a383a7faf632a50c2298c9c65aa0b2
Author: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Date: Thu Sep 28 01:45:21 2006 +0100
[MIPS] Improve branch prediction in ll/sc atomic operations.
Now that finally all supported versions of binutils have functioning
support for .subsection use .subsection to tweak the branch prediction
I did not modify the R10000 errata variants because it seems unclear if
this will invalidate the workaround which actually relies on the cheesy
prediction of branch likely to cause a misspredict if the sc was
successful.
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
diff --git a/include/asm-mips/atomic.h b/include/asm-mips/atomic.h
index e64abc0..91bf6a7 100644
--- a/include/asm-mips/atomic.h
+++ b/include/asm-mips/atomic.h
@@ -9,7 +9,7 @@
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
- * Copyright (C) 1996, 97, 99, 2000, 03, 04 by Ralf Baechle
+ * Copyright (C) 1996, 97, 99, 2000, 03, 04, 06 Ralf Baechle
*/
/*
@@ -76,7 +76,10 @@ static __inline__ void atomic_add(int i,
"1: ll %0, %1 # atomic_add \n"
" addu %0, %2 \n"
" sc %0, %1 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter));
@@ -118,7 +121,10 @@ static __inline__ void atomic_sub(int i,
"1: ll %0, %1 # atomic_sub \n"
" subu %0, %2 \n"
" sc %0, %1 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter));
@@ -161,9 +167,12 @@ static __inline__ int atomic_add_return(
"1: ll %1, %2 # atomic_add_return \n"
" addu %0, %1, %3 \n"
" sc %0, %2 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
" addu %0, %1, %3 \n"
" sync \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (result), "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter)
@@ -208,9 +217,12 @@ static __inline__ int atomic_sub_return(
"1: ll %1, %2 # atomic_sub_return \n"
" subu %0, %1, %3 \n"
" sc %0, %2 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
" subu %0, %1, %3 \n"
" sync \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (result), "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter)
@@ -269,11 +281,14 @@ static __inline__ int atomic_sub_if_posi
" bltz %0, 1f \n"
" sc %0, %2 \n"
" .set noreorder \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
" subu %0, %1, %3 \n"
" .set reorder \n"
" sync \n"
"1: \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (result), "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter)
@@ -430,7 +445,10 @@ static __inline__ void atomic64_add(long
"1: lld %0, %1 # atomic64_add \n"
" addu %0, %2 \n"
" scd %0, %1 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter));
@@ -472,7 +490,10 @@ static __inline__ void atomic64_sub(long
"1: lld %0, %1 # atomic64_sub \n"
" subu %0, %2 \n"
" scd %0, %1 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter));
@@ -515,9 +536,12 @@ static __inline__ long atomic64_add_retu
"1: lld %1, %2 # atomic64_add_return \n"
" addu %0, %1, %3 \n"
" scd %0, %2 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
" addu %0, %1, %3 \n"
" sync \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (result), "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter)
@@ -562,9 +586,12 @@ static __inline__ long atomic64_sub_retu
"1: lld %1, %2 # atomic64_sub_return \n"
" subu %0, %1, %3 \n"
" scd %0, %2 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
" subu %0, %1, %3 \n"
" sync \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (result), "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter)
@@ -623,11 +650,14 @@ static __inline__ long atomic64_sub_if_p
" bltz %0, 1f \n"
" scd %0, %2 \n"
" .set noreorder \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
" dsubu %0, %1, %3 \n"
" .set reorder \n"
" sync \n"
"1: \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (result), "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter)
diff --git a/include/asm-mips/bitops.h b/include/asm-mips/bitops.h
index 1bb89c5..d10bd56 100644
--- a/include/asm-mips/bitops.h
+++ b/include/asm-mips/bitops.h
@@ -3,7 +3,7 @@
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
- * Copyright (c) 1994 - 1997, 1999, 2000 Ralf Baechle (ralf@xxxxxxx)
+ * Copyright (c) 1994 - 1997, 1999, 2000, 06 Ralf Baechle (ralf@xxxxxxxxxxxxxx)
* Copyright (c) 1999, 2000 Silicon Graphics, Inc.
*/
#ifndef _ASM_BITOPS_H
@@ -86,7 +86,10 @@ static inline void set_bit(unsigned long
"1: " __LL "%0, %1 # set_bit \n"
" or %0, %2 \n"
" " __SC "%0, %1 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (temp), "=m" (*m)
: "ir" (1UL << (nr & SZLONG_MASK)), "m" (*m));
@@ -134,7 +137,10 @@ static inline void clear_bit(unsigned lo
"1: " __LL "%0, %1 # clear_bit \n"
" and %0, %2 \n"
" " __SC "%0, %1 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (temp), "=m" (*m)
: "ir" (~(1UL << (nr & SZLONG_MASK))), "m" (*m));
@@ -184,7 +190,10 @@ static inline void change_bit(unsigned l
"1: " __LL "%0, %1 # change_bit \n"
" xor %0, %2 \n"
" " __SC "%0, %1 \n"
- " beqz %0, 1b \n"
+ " beqz %0, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (temp), "=m" (*m)
: "ir" (1UL << (nr & SZLONG_MASK)), "m" (*m));
@@ -243,11 +252,14 @@ #endif
"1: " __LL "%0, %1 # test_and_set_bit \n"
" or %2, %0, %3 \n"
" " __SC "%2, %1 \n"
- " beqz %2, 1b \n"
+ " beqz %2, 2f \n"
" and %2, %0, %3 \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (temp), "=m" (*m), "=&r" (res)
: "r" (1UL << (nr & SZLONG_MASK)), "m" (*m)
@@ -315,11 +327,14 @@ #endif
" or %2, %0, %3 \n"
" xor %2, %3 \n"
" " __SC "%2, %1 \n"
- " beqz %2, 1b \n"
+ " beqz %2, 2f \n"
" and %2, %0, %3 \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (temp), "=m" (*m), "=&r" (res)
: "r" (1UL << (nr & SZLONG_MASK)), "m" (*m)
@@ -385,11 +400,14 @@ #endif
"1: " __LL "%0, %1 # test_and_change_bit \n"
" xor %2, %0, %3 \n"
" " __SC "\t%2, %1 \n"
- " beqz %2, 1b \n"
+ " beqz %2, 2f \n"
" and %2, %0, %3 \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (temp), "=m" (*m), "=&r" (res)
: "r" (1UL << (nr & SZLONG_MASK)), "m" (*m)
diff --git a/include/asm-mips/spinlock.h b/include/asm-mips/spinlock.h
index 4c1a1b5..3df6103 100644
--- a/include/asm-mips/spinlock.h
+++ b/include/asm-mips/spinlock.h
@@ -3,7 +3,7 @@
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
- * Copyright (C) 1999, 2000 by Ralf Baechle
+ * Copyright (C) 1999, 2000, 06 Ralf Baechle (ralf@xxxxxxxxxxxxxx)
* Copyright (C) 1999, 2000 Silicon Graphics, Inc.
*/
#ifndef _ASM_SPINLOCK_H
@@ -49,11 +49,18 @@ static inline void __raw_spin_lock(raw_s
__asm__ __volatile__(
" .set noreorder # __raw_spin_lock \n"
"1: ll %1, %2 \n"
- " bnez %1, 1b \n"
+ " bnez %1, 2f \n"
" li %1, 1 \n"
" sc %1, %0 \n"
- " beqz %1, 1b \n"
+ " beqz %1, 2f \n"
" sync \n"
+ " .subsection 2 \n"
+ "2: ll %1, %2 \n"
+ " bnez %1, 2b \n"
+ " li %1, 1 \n"
+ " b 1b \n"
+ " nop \n"
+ " .previous \n"
" .set reorder \n"
: "=m" (lock->lock), "=&r" (tmp)
: "m" (lock->lock)
@@ -97,9 +104,12 @@ static inline unsigned int __raw_spin_tr
"1: ll %0, %3 \n"
" ori %2, %0, 1 \n"
" sc %2, %1 \n"
- " beqz %2, 1b \n"
+ " beqz %2, 2f \n"
" andi %2, %0, 1 \n"
" sync \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set reorder"
: "=&r" (temp), "=m" (lock->lock), "=&r" (res)
: "m" (lock->lock)
@@ -152,11 +162,17 @@ static inline void __raw_read_lock(raw_r
__asm__ __volatile__(
" .set noreorder # __raw_read_lock \n"
"1: ll %1, %2 \n"
- " bltz %1, 1b \n"
+ " bltz %1, 2f \n"
" addu %1, 1 \n"
" sc %1, %0 \n"
" beqz %1, 1b \n"
" sync \n"
+ " .subsection 2 \n"
+ "2: ll %1, %2 \n"
+ " bltz %1, 2b \n"
+ " addu %1, 1 \n"
+ " b 1b \n"
+ " .previous \n"
" .set reorder \n"
: "=m" (rw->lock), "=&r" (tmp)
: "m" (rw->lock)
@@ -187,8 +203,10 @@ static inline void __raw_read_unlock(raw
"1: ll %1, %2 \n"
" sub %1, 1 \n"
" sc %1, %0 \n"
- " beqz %1, 1b \n"
+ " beqz %1, 2f \n"
" sync \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
" .set reorder \n"
: "=m" (rw->lock), "=&r" (tmp)
: "m" (rw->lock)
@@ -217,11 +235,17 @@ static inline void __raw_write_lock(raw_
__asm__ __volatile__(
" .set noreorder # __raw_write_lock \n"
"1: ll %1, %2 \n"
- " bnez %1, 1b \n"
+ " bnez %1, 2f \n"
" lui %1, 0x8000 \n"
" sc %1, %0 \n"
- " beqz %1, 1b \n"
+ " beqz %1, 2f \n"
" sync \n"
+ " .subsection 2 \n"
+ "2: ll %1, %2 \n"
+ " bnez %1, 1b \n"
+ " lui %1, 0x8000 \n"
+ " b 1b \n"
+ " .previous \n"
" .set reorder \n"
: "=m" (rw->lock), "=&r" (tmp)
: "m" (rw->lock)
@@ -314,11 +338,15 @@ static inline int __raw_write_trylock(ra
" bnez %1, 2f \n"
" lui %1, 0x8000 \n"
" sc %1, %0 \n"
- " beqz %1, 1b \n"
- " sync \n"
- " li %2, 1 \n"
- " .set reorder \n"
+ " beqz %1, 3f \n"
+ " li %2, 1 \n"
"2: \n"
+ " sync \n"
+ " .subsection 2 \n"
+ "3: b 1b \n"
+ " li %2, 0 \n"
+ " .previous \n"
+ " .set reorder \n"
: "=m" (rw->lock), "=&r" (tmp), "=&r" (ret)
: "m" (rw->lock)
: "memory");
diff --git a/include/asm-mips/system.h b/include/asm-mips/system.h
index dcb4701..fc35526 100644
--- a/include/asm-mips/system.h
+++ b/include/asm-mips/system.h
@@ -3,7 +3,7 @@
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
- * Copyright (C) 1994, 95, 96, 97, 98, 99, 2003 by Ralf Baechle
+ * Copyright (C) 1994, 95, 96, 97, 98, 99, 2003, 06 by Ralf Baechle
* Copyright (C) 1996 by Paul M. Antoine
* Copyright (C) 1999 Silicon Graphics
* Kevin D. Kissell, kevink@xxxxxxxx and Carsten Langgaard, carstenl@xxxxxxxx
@@ -234,10 +234,13 @@ #endif
" move %2, %z4 \n"
" .set mips3 \n"
" sc %2, %1 \n"
- " beqz %2, 1b \n"
+ " beqz %2, 2f \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (retval), "=m" (*m), "=&r" (dummy)
: "R" (*m), "Jr" (val)
@@ -283,10 +286,13 @@ #endif
"1: lld %0, %3 # xchg_u64 \n"
" move %2, %z4 \n"
" scd %2, %1 \n"
- " beqz %2, 1b \n"
+ " beqz %2, 2f \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (retval), "=m" (*m), "=&r" (dummy)
: "R" (*m), "Jr" (val)
@@ -364,11 +370,14 @@ #endif
" move $1, %z4 \n"
" .set mips3 \n"
" sc $1, %1 \n"
- " beqz $1, 1b \n"
+ " beqz $1, 3f \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
"2: \n"
+ " .subsection 2 \n"
+ "3: b 1b \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (retval), "=R" (*m)
: "R" (*m), "Jr" (old), "Jr" (new)
@@ -419,11 +428,14 @@ #endif
" bne %0, %z3, 2f \n"
" move $1, %z4 \n"
" scd $1, %1 \n"
- " beqz $1, 1b \n"
+ " beqz $1, 3f \n"
#ifdef CONFIG_SMP
" sync \n"
#endif
"2: \n"
+ " .subsection 2 \n"
+ "3: b 1b \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (retval), "=R" (*m)
: "R" (*m), "Jr" (old), "Jr" (new)
