在 2016年04月07日 02:44, Sam Ravnborg 写道:
Hi Zeng.
Use runtime patching for sparc64, lifted from hweight
No errors found in patch - but a few comments.
In general patch looks good.
Thanks. Sparc, powerpc, and x86 are all new to me.
+++ b/arch/sparc/include/asm/bitops_64.h
@@ -47,6 +47,24 @@ unsigned int __arch_hweight16(unsigned int w);
unsigned int __arch_hweight8(unsigned int w);
#include <asm-generic/bitops/const_hweight.h>
+
+/*
+ * parityN: returns the parity of a N-bit word,
+ * i.e. the number of 1-bits in w modulo 2.
+ */
+
+static inline unsigned int __arch_parity4(unsigned int w)
+{
+ w &= 0xf;
+ return (0x6996 >> w) & 1;
+}
As Josef already said - this constant should have a name.
PARITY_BIT
?
Maybe PARITY_MAGIC?
+++ b/arch/sparc/kernel/sparc_ksyms_64.c
@@ -45,6 +45,12 @@ EXPORT_SYMBOL(__arch_hweight16);
EXPORT_SYMBOL(__arch_hweight32);
EXPORT_SYMBOL(__arch_hweight64);
+/* from parity.S */
+EXPORT_SYMBOL(__arch_parity8);
+EXPORT_SYMBOL(__arch_parity16);
+EXPORT_SYMBOL(__arch_parity32);
+EXPORT_SYMBOL(__arch_parity64);
Did you compile this?
I wonder if bitops_64.h is indirectly included.
Yes.
index 0000000..b1945e3
--- /dev/null
+++ b/arch/sparc/lib/parity.S
@@ -0,0 +1,93 @@
+#include <linux/linkage.h>
+
+ .text
+ .align 32
+
+ENTRY(__arch_parity8)
+ srl %o0, 4, %g1
+ xor %o0, %g1, %o0
+ and %o0, 0xf, %o0
+ sethi %hi(0x6996), %g1
+ or %g1, %lo(0x6996), %g1
+ srl %g1, %o0, %o0
+ retl
+ and %o0, 1, %o0
+ENDPROC(__arch_parity8)
I know the level of comments in hweight is equal to none.
But please do not follow this bad example.
At least for each function a one-liner of the C code.
And in the top of the file maybe two lines that the functions
are patched at run-time if the processor has popc available.
Sam
OK. I will try, but my english is very poor! :-)
--
To unsubscribe from this list: send the line "unsubscribe sparclinux" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
