x86, asm: use bool for bitops and other assembly outputs
The gcc people have confirmed that using "bool" when combined with
inline assembly always is treated as a byte-sized operand that can be
assumed to be 0 or 1, which is exactly what the SET instruction
emits. Change the output types and intermediate variables of as many
operations as practical to "bool".
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1465414726-197858-3-git-send-email-hpa@linux.intel.com
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h
index b2b797d..8cbb7f4 100644
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -201,7 +201,7 @@
* This operation is atomic and cannot be reordered.
* It also implies a memory barrier.
*/
-static __always_inline int test_and_set_bit(long nr, volatile unsigned long *addr)
+static __always_inline bool test_and_set_bit(long nr, volatile unsigned long *addr)
{
GEN_BINARY_RMWcc(LOCK_PREFIX "bts", *addr, "Ir", nr, "%0", "c");
}
@@ -213,7 +213,7 @@
*
* This is the same as test_and_set_bit on x86.
*/
-static __always_inline int
+static __always_inline bool
test_and_set_bit_lock(long nr, volatile unsigned long *addr)
{
return test_and_set_bit(nr, addr);
@@ -228,9 +228,9 @@
* If two examples of this operation race, one can appear to succeed
* but actually fail. You must protect multiple accesses with a lock.
*/
-static __always_inline int __test_and_set_bit(long nr, volatile unsigned long *addr)
+static __always_inline bool __test_and_set_bit(long nr, volatile unsigned long *addr)
{
- unsigned char oldbit;
+ bool oldbit;
asm("bts %2,%1\n\t"
"setc %0"
@@ -247,7 +247,7 @@
* This operation is atomic and cannot be reordered.
* It also implies a memory barrier.
*/
-static __always_inline int test_and_clear_bit(long nr, volatile unsigned long *addr)
+static __always_inline bool test_and_clear_bit(long nr, volatile unsigned long *addr)
{
GEN_BINARY_RMWcc(LOCK_PREFIX "btr", *addr, "Ir", nr, "%0", "c");
}
@@ -268,9 +268,9 @@
* accessed from a hypervisor on the same CPU if running in a VM: don't change
* this without also updating arch/x86/kernel/kvm.c
*/
-static __always_inline int __test_and_clear_bit(long nr, volatile unsigned long *addr)
+static __always_inline bool __test_and_clear_bit(long nr, volatile unsigned long *addr)
{
- unsigned char oldbit;
+ bool oldbit;
asm volatile("btr %2,%1\n\t"
"setc %0"
@@ -280,9 +280,9 @@
}
/* WARNING: non atomic and it can be reordered! */
-static __always_inline int __test_and_change_bit(long nr, volatile unsigned long *addr)
+static __always_inline bool __test_and_change_bit(long nr, volatile unsigned long *addr)
{
- unsigned char oldbit;
+ bool oldbit;
asm volatile("btc %2,%1\n\t"
"setc %0"
@@ -300,20 +300,20 @@
* This operation is atomic and cannot be reordered.
* It also implies a memory barrier.
*/
-static __always_inline int test_and_change_bit(long nr, volatile unsigned long *addr)
+static __always_inline bool test_and_change_bit(long nr, volatile unsigned long *addr)
{
GEN_BINARY_RMWcc(LOCK_PREFIX "btc", *addr, "Ir", nr, "%0", "c");
}
-static __always_inline int constant_test_bit(long nr, const volatile unsigned long *addr)
+static __always_inline bool constant_test_bit(long nr, const volatile unsigned long *addr)
{
return ((1UL << (nr & (BITS_PER_LONG-1))) &
(addr[nr >> _BITOPS_LONG_SHIFT])) != 0;
}
-static __always_inline int variable_test_bit(long nr, volatile const unsigned long *addr)
+static __always_inline bool variable_test_bit(long nr, volatile const unsigned long *addr)
{
- unsigned char oldbit;
+ bool oldbit;
asm volatile("bt %2,%1\n\t"
"setc %0"
@@ -329,7 +329,7 @@
* @nr: bit number to test
* @addr: Address to start counting from
*/
-static int test_bit(int nr, const volatile unsigned long *addr);
+static bool test_bit(int nr, const volatile unsigned long *addr);
#endif
#define test_bit(nr, addr) \