[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>
diff --git a/include/asm-mips/atomic.h b/include/asm-mips/atomic.h
index c1a2409..8578869 100644
--- a/include/asm-mips/atomic.h
+++ b/include/asm-mips/atomic.h
@@ -69,7 +69,10 @@
"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));
@@ -111,7 +114,10 @@
"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));
@@ -155,8 +161,11 @@
"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"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (result), "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter)
@@ -204,8 +213,11 @@
"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"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (result), "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter)
@@ -267,10 +279,13 @@
" 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"
"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)
@@ -429,7 +444,10 @@
"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));
@@ -471,7 +489,10 @@
"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));
@@ -515,8 +536,11 @@
"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"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (result), "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter)
@@ -564,8 +588,11 @@
"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"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (result), "=&r" (temp), "=m" (v->counter)
: "Ir" (i), "m" (v->counter)
@@ -627,10 +654,13 @@
" 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"
"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 06445de..06c0822 100644
--- a/include/asm-mips/bitops.h
+++ b/include/asm-mips/bitops.h
@@ -68,7 +68,10 @@
"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));
@@ -116,7 +119,10 @@
"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));
@@ -166,7 +172,10 @@
"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));
@@ -222,8 +231,12 @@
"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"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " nop \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (temp), "=m" (*m), "=&r" (res)
: "r" (1UL << (nr & SZLONG_MASK)), "m" (*m)
@@ -290,8 +303,12 @@
" 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"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " nop \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (temp), "=m" (*m), "=&r" (res)
: "r" (1UL << (nr & SZLONG_MASK)), "m" (*m)
@@ -356,8 +373,12 @@
"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"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " nop \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 fc3217f..f1755d2 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 @@
__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 @@
"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 @@
__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 @@
"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 @@
__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 @@
" 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");
diff --git a/include/asm-mips/system.h b/include/asm-mips/system.h
index 5e1289c..597a374 100644
--- a/include/asm-mips/system.h
+++ b/include/asm-mips/system.h
@@ -110,7 +110,10 @@
" move %2, %z4 \n"
" .set mips3 \n"
" sc %2, %1 \n"
- " beqz %2, 1b \n"
+ " beqz %2, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (retval), "=m" (*m), "=&r" (dummy)
: "R" (*m), "Jr" (val)
@@ -155,7 +158,10 @@
"1: lld %0, %3 # xchg_u64 \n"
" move %2, %z4 \n"
" scd %2, %1 \n"
- " beqz %2, 1b \n"
+ " beqz %2, 2f \n"
+ " .subsection 2 \n"
+ "2: b 1b \n"
+ " .previous \n"
" .set mips0 \n"
: "=&r" (retval), "=m" (*m), "=&r" (dummy)
: "R" (*m), "Jr" (val)
@@ -232,8 +238,11 @@
" move $1, %z4 \n"
" .set mips3 \n"
" sc $1, %1 \n"
- " beqz $1, 1b \n"
+ " beqz $1, 3f \n"
"2: \n"
+ " .subsection 2 \n"
+ "3: b 1b \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (retval), "=R" (*m)
: "R" (*m), "Jr" (old), "Jr" (new)
@@ -283,8 +292,11 @@
" bne %0, %z3, 2f \n"
" move $1, %z4 \n"
" scd $1, %1 \n"
- " beqz $1, 1b \n"
+ " beqz $1, 3f \n"
"2: \n"
+ " .subsection 2 \n"
+ "3: b 1b \n"
+ " .previous \n"
" .set pop \n"
: "=&r" (retval), "=R" (*m)
: "R" (*m), "Jr" (old), "Jr" (new)
