xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

[MIPS] Improve branch prediction in ll/sc atomic operations.

Browse Source 
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>
This commit is contained in:
Ralf Baechle
2006-09-28 01:45:21 +01:00
parent 509cb37e17
commit f65e4fa8e0
4 changed files with 128 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

58
include/asm-mips/spinlock.h
View File

@@ -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"
__WEAK_ORDERING_MB
" li %2, 1 \n"
" .set reorder \n"
" beqz %1, 3f \n"
" li %2, 1 \n"
"2: \n"
__WEAK_ORDERING_MB
" .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");