diff mbox series

[18/37] MIPS: bitops: Only use ins for bit 16 or higher

Message ID 20190930230806.2940505-19-paul.burton@mips.com (mailing list archive)
State Superseded
Headers show
Series MIPS: barriers & atomics cleanups | expand

Commit Message

Paul Burton Sept. 30, 2019, 11:08 p.m. UTC 
set_bit() can set bits 0-15 using an ori instruction, rather than
loading the value -1 into a register & then using an ins instruction.

That is, rather than the following:

  li   t0, -1
  ll   t1, 0(t2)
  ins  t1, t0, 4, 1
  sc   t1, 0(t2)

We can have the simpler:

  ll   t1, 0(t2)
  ori  t1, t1, 0x10
  sc   t1, 0(t2)

The or path already allows immediates to be used, so simply restricting
the ins path to bits that don't fit in immediates is sufficient to take
advantage of this.

Signed-off-by: Paul Burton <paul.burton@mips.com>
---

 arch/mips/include/asm/bitops.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/mips/include/asm/bitops.h b/arch/mips/include/asm/bitops.h
index d3f3f37ca0b1..3ea4f172ac08 100644
--- a/arch/mips/include/asm/bitops.h
+++ b/arch/mips/include/asm/bitops.h
@@ -77,7 +77,7 @@  static inline void set_bit(unsigned long nr, volatile unsigned long *addr)
 	}
 
 #if defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR6)
-	if (__builtin_constant_p(bit)) {
+	if (__builtin_constant_p(bit) && (bit >= 16)) {
 		loongson_llsc_mb();
 		do {
 			__asm__ __volatile__(