Commit de60c1a1 authored by Vineet Gupta's avatar Vineet Gupta
Browse files

ARC: fold __builtin_constant_p() into test_bit() 



This makes test_bit() more like its siblings *_bit() routines.
Also add some comments about the constant @nr micro-optimization

Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
parent 0dfb8ec7

arch/arc/include/asm/bitops.h

+18 −13
Original line number Diff line number Diff line
@@ -32,6 +32,20 @@ static inline void set_bit(unsigned long nr, volatile unsigned long *m) 


	m += nr >> 5;



	/*

	 * ARC ISA micro-optimization:

	 *

	 * Instructions dealing with bitpos only consider lower 5 bits (0-31)

	 * e.g (x << 33) is handled like (x << 1) by ASL instruction

	 *  (mem pointer still needs adjustment to point to next word)

	 *

	 * Hence the masking to clamp @nr arg can be elided in general.

	 *

	 * However if @nr is a constant (above assumed it in a register),

	 * and greater than 31, gcc can optimize away (x << 33) to 0,

	 * as overflow, given the 32-bit ISA. Thus masking needs to be done

	 * for constant @nr, but no code is generated due to const prop.

	 */

	if (__builtin_constant_p(nr))

		nr &= 0x1f;
@@ -374,29 +388,20 @@ __test_and_change_bit(unsigned long nr, volatile unsigned long *m) 
 * This routine doesn't need to be atomic.

 */

static inline int

__constant_test_bit(unsigned int nr, const volatile unsigned long *addr)

{

	return ((1UL << (nr & 31)) &

		(((const volatile unsigned int *)addr)[nr >> 5])) != 0;

}



static inline int

__test_bit(unsigned int nr, const volatile unsigned long *addr)

test_bit(unsigned int nr, const volatile unsigned long *addr)

{

	unsigned long mask;



	addr += nr >> 5;



	/* ARC700 only considers 5 bits in bit-fiddling insn */

	if (__builtin_constant_p(nr))

		nr &= 0x1f;



	mask = 1 << nr;



	return ((mask & *addr) != 0);

}



#define test_bit(nr, addr)	(__builtin_constant_p(nr) ? \

					__constant_test_bit((nr), (addr)) : \

					__test_bit((nr), (addr)))



/*

 * Count the number of zeros, starting from MSB

 * Helper for fls( ) friends