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authorRalf Baechle <ralf@linux-mips.org>2006-09-28 01:45:21 +0100
committerRalf Baechle <ralf@linux-mips.org>2007-02-13 22:40:50 +0000
commitf65e4fa8e0c6022ad58dc88d1b11b12589ed7f9f (patch)
tree2405e012e079693e0fcfde9ff981c549d6c68a21 /include/asm-mips/spinlock.h
parent509cb37e173d4e39cec47238397e91b718730794 (diff)
[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@linux-mips.org>
Diffstat (limited to 'include/asm-mips/spinlock.h')
-rw-r--r--include/asm-mips/spinlock.h56
1 files changed, 44 insertions, 12 deletions
diff --git a/include/asm-mips/spinlock.h b/include/asm-mips/spinlock.h
index fc3217fc111..f1755d28a36 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, 06 by Ralf Baechle
+ * Copyright (C) 1999, 2000, 06 Ralf Baechle (ralf@linux-mips.org)
* Copyright (C) 1999, 2000 Silicon Graphics, Inc.
*/
#ifndef _ASM_SPINLOCK_H
@@ -49,11 +49,18 @@ static inline void __raw_spin_lock(raw_spinlock_t *lock)
__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"
" nop \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)
@@ -99,8 +106,12 @@ static inline unsigned int __raw_spin_trylock(raw_spinlock_t *lock)
"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"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " nop \n"
+ " .previous \n"
" .set reorder"
: "=&r" (temp), "=m" (lock->lock), "=&r" (res)
: "m" (lock->lock)
@@ -154,11 +165,18 @@ static inline void __raw_read_lock(raw_rwlock_t *rw)
__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"
" nop \n"
+ " .subsection 2 \n"
+ "2: ll %1, %2 \n"
+ " bltz %1, 2b \n"
+ " addu %1, 1 \n"
+ " b 1b \n"
+ " nop \n"
+ " .previous \n"
" .set reorder \n"
: "=m" (rw->lock), "=&r" (tmp)
: "m" (rw->lock)
@@ -192,8 +210,12 @@ static inline void __raw_read_unlock(raw_rwlock_t *rw)
"1: ll %1, %2 \n"
" sub %1, 1 \n"
" sc %1, %0 \n"
- " beqz %1, 1b \n"
+ " beqz %1, 2f \n"
+ " nop \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
" nop \n"
+ " .previous \n"
" .set reorder \n"
: "=m" (rw->lock), "=&r" (tmp)
: "m" (rw->lock)
@@ -222,11 +244,18 @@ static inline void __raw_write_lock(raw_rwlock_t *rw)
__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"
+ " nop \n"
+ " .subsection 2 \n"
+ "2: ll %1, %2 \n"
+ " bnez %1, 2b \n"
+ " lui %1, 0x8000 \n"
+ " b 1b \n"
" nop \n"
+ " .previous \n"
" .set reorder \n"
: "=m" (rw->lock), "=&r" (tmp)
: "m" (rw->lock)
@@ -322,12 +351,15 @@ static inline int __raw_write_trylock(raw_rwlock_t *rw)
" bnez %1, 2f \n"
" lui %1, 0x8000 \n"
" sc %1, %0 \n"
- " beqz %1, 1b \n"
- " nop \n"
+ " beqz %1, 3f \n"
+ " li %2, 1 \n"
+ "2: \n"
__WEAK_ORDERING_MB
- " li %2, 1 \n"
+ " .subsection 2 \n"
+ "3: b 1b \n"
+ " li %2, 0 \n"
+ " .previous \n"
" .set reorder \n"
- "2: \n"
: "=m" (rw->lock), "=&r" (tmp), "=&r" (ret)
: "m" (rw->lock)
: "memory");