| Message ID | 20250223164217.2139331-4-visitorckw@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Introduce and use generic parity32/64 helper | expand |
On 23. 02. 25 17:42, Kuan-Wei Chiu wrote: > Refactor parity calculations to use the standard parity8() helper. This > change eliminates redundant implementations and improves code > efficiency. The patch improves parity assembly code in bootflag.o from: 58: 89 de mov %ebx,%esi 5a: b9 08 00 00 00 mov $0x8,%ecx 5f: 31 d2 xor %edx,%edx 61: 89 f0 mov %esi,%eax 63: 89 d7 mov %edx,%edi 65: 40 d0 ee shr %sil 68: 83 e0 01 and $0x1,%eax 6b: 31 c2 xor %eax,%edx 6d: 83 e9 01 sub $0x1,%ecx 70: 75 ef jne 61 <sbf_init+0x51> 72: 39 c7 cmp %eax,%edi 74: 74 7f je f5 <sbf_init+0xe5> 76: to: 54: 89 d8 mov %ebx,%eax 56: ba 96 69 00 00 mov $0x6996,%edx 5b: c0 e8 04 shr $0x4,%al 5e: 31 d8 xor %ebx,%eax 60: 83 e0 0f and $0xf,%eax 63: 0f a3 c2 bt %eax,%edx 66: 73 64 jae cc <sbf_init+0xbc> 68: which is faster and smaller (-10 bytes) code. Reviewed-by: Uros Bizjak <ubizjak@gmail.com> Thanks, Uros. > > Co-developed-by: Yu-Chun Lin <eleanor15x@gmail.com> > Signed-off-by: Yu-Chun Lin <eleanor15x@gmail.com> > Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com> > --- > arch/x86/kernel/bootflag.c | 18 +++--------------- > 1 file changed, 3 insertions(+), 15 deletions(-) > > diff --git a/arch/x86/kernel/bootflag.c b/arch/x86/kernel/bootflag.c > index 3fed7ae58b60..314ff0e84900 100644 > --- a/arch/x86/kernel/bootflag.c > +++ b/arch/x86/kernel/bootflag.c > @@ -8,6 +8,7 @@ > #include <linux/string.h> > #include <linux/spinlock.h> > #include <linux/acpi.h> > +#include <linux/bitops.h> > #include <asm/io.h> > > #include <linux/mc146818rtc.h> > @@ -20,26 +21,13 @@ > > int sbf_port __initdata = -1; /* set via acpi_boot_init() */ > > -static int __init parity(u8 v) > -{ > - int x = 0; > - int i; > - > - for (i = 0; i < 8; i++) { > - x ^= (v & 1); > - v >>= 1; > - } > - > - return x; > -} > - > static void __init sbf_write(u8 v) > { > unsigned long flags; > > if (sbf_port != -1) { > v &= ~SBF_PARITY; > - if (!parity(v)) > + if (!parity8(v)) > v |= SBF_PARITY; > > printk(KERN_INFO "Simple Boot Flag at 0x%x set to 0x%x\n", > @@ -70,7 +58,7 @@ static int __init sbf_value_valid(u8 v) > { > if (v & SBF_RESERVED) /* Reserved bits */ > return 0; > - if (!parity(v)) > + if (!parity8(v)) > return 0; > > return 1;
diff --git a/arch/x86/kernel/bootflag.c b/arch/x86/kernel/bootflag.c index 3fed7ae58b60..314ff0e84900 100644 --- a/arch/x86/kernel/bootflag.c +++ b/arch/x86/kernel/bootflag.c @@ -8,6 +8,7 @@ #include <linux/string.h> #include <linux/spinlock.h> #include <linux/acpi.h> +#include <linux/bitops.h> #include <asm/io.h> #include <linux/mc146818rtc.h> @@ -20,26 +21,13 @@ int sbf_port __initdata = -1; /* set via acpi_boot_init() */ -static int __init parity(u8 v) -{ - int x = 0; - int i; - - for (i = 0; i < 8; i++) { - x ^= (v & 1); - v >>= 1; - } - - return x; -} - static void __init sbf_write(u8 v) { unsigned long flags; if (sbf_port != -1) { v &= ~SBF_PARITY; - if (!parity(v)) + if (!parity8(v)) v |= SBF_PARITY; printk(KERN_INFO "Simple Boot Flag at 0x%x set to 0x%x\n", @@ -70,7 +58,7 @@ static int __init sbf_value_valid(u8 v) { if (v & SBF_RESERVED) /* Reserved bits */ return 0; - if (!parity(v)) + if (!parity8(v)) return 0; return 1;