From f782ddf297318d544bf71ee1e8afbac8d55f1878 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Fri, 21 Apr 2017 13:18:52 +0200 Subject: [PATCH] powerpc: Remove __ilog2()s and use generic ones With the __ilog2() function as defined in arch/powerpc/include/asm/bitops.h, GCC will not optimise the code in case of constant parameter. The generic ilog2() function in include/linux/log2.h is written to handle the case of the constant parameter. This patch discards the three __ilog2() functions and defines __ilog2() as ilog2() For non constant calls, the generated code is doing the same: int test__ilog2(unsigned long x) { return __ilog2(x); } int test__ilog2_u32(u32 n) { return __ilog2_u32(n); } int test__ilog2_u64(u64 n) { return __ilog2_u64(n); } On PPC32 before the patch: 00000000 : 0: 7c 63 00 34 cntlzw r3,r3 4: 20 63 00 1f subfic r3,r3,31 8: 4e 80 00 20 blr 0000000c : c: 7c 63 00 34 cntlzw r3,r3 10: 20 63 00 1f subfic r3,r3,31 14: 4e 80 00 20 blr On PPC32 after the patch: 00000000 : 0: 7c 63 00 34 cntlzw r3,r3 4: 20 63 00 1f subfic r3,r3,31 8: 4e 80 00 20 blr 0000000c : c: 7c 63 00 34 cntlzw r3,r3 10: 20 63 00 1f subfic r3,r3,31 14: 4e 80 00 20 blr On PPC64 before the patch: 0000000000000000 <.test__ilog2>: 0: 7c 63 00 74 cntlzd r3,r3 4: 20 63 00 3f subfic r3,r3,63 8: 7c 63 07 b4 extsw r3,r3 c: 4e 80 00 20 blr 0000000000000010 <.test__ilog2_u32>: 10: 7c 63 00 34 cntlzw r3,r3 14: 20 63 00 1f subfic r3,r3,31 18: 7c 63 07 b4 extsw r3,r3 1c: 4e 80 00 20 blr 0000000000000020 <.test__ilog2_u64>: 20: 7c 63 00 74 cntlzd r3,r3 24: 20 63 00 3f subfic r3,r3,63 28: 7c 63 07 b4 extsw r3,r3 2c: 4e 80 00 20 blr On PPC64 after the patch: 0000000000000000 <.test__ilog2>: 0: 7c 63 00 74 cntlzd r3,r3 4: 20 63 00 3f subfic r3,r3,63 8: 7c 63 07 b4 extsw r3,r3 c: 4e 80 00 20 blr 0000000000000010 <.test__ilog2_u32>: 10: 7c 63 00 34 cntlzw r3,r3 14: 20 63 00 1f subfic r3,r3,31 18: 7c 63 07 b4 extsw r3,r3 1c: 4e 80 00 20 blr 0000000000000020 <.test__ilog2_u64>: 20: 7c 63 00 74 cntlzd r3,r3 24: 20 63 00 3f subfic r3,r3,63 28: 7c 63 07 b4 extsw r3,r3 2c: 4e 80 00 20 blr Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman --- arch/powerpc/Kconfig | 8 -------- arch/powerpc/include/asm/bitops.h | 27 +-------------------------- 2 files changed, 1 insertion(+), 34 deletions(-) diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 0153275e9f75..b50d46d214f6 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -109,14 +109,6 @@ config GENERIC_LOCKBREAK default y depends on SMP && PREEMPT -config ARCH_HAS_ILOG2_U32 - bool - default y - -config ARCH_HAS_ILOG2_U64 - bool - default y if 64BIT - config GENERIC_HWEIGHT bool default y diff --git a/arch/powerpc/include/asm/bitops.h b/arch/powerpc/include/asm/bitops.h index d835cd697d6b..b750ffef83c7 100644 --- a/arch/powerpc/include/asm/bitops.h +++ b/arch/powerpc/include/asm/bitops.h @@ -206,32 +206,7 @@ static __inline__ void __clear_bit_unlock(int nr, volatile unsigned long *addr) * Return the zero-based bit position (LE, not IBM bit numbering) of * the most significant 1-bit in a double word. */ -static __inline__ __attribute__((const)) -int __ilog2(unsigned long x) -{ - int lz; - - asm (PPC_CNTLZL "%0,%1" : "=r" (lz) : "r" (x)); - return BITS_PER_LONG - 1 - lz; -} - -static inline __attribute__((const)) -int __ilog2_u32(u32 n) -{ - int bit; - asm ("cntlzw %0,%1" : "=r" (bit) : "r" (n)); - return 31 - bit; -} - -#ifdef __powerpc64__ -static inline __attribute__((const)) -int __ilog2_u64(u64 n) -{ - int bit; - asm ("cntlzd %0,%1" : "=r" (bit) : "r" (n)); - return 63 - bit; -} -#endif +#define __ilog2(x) ilog2(x) #include