patch-2.4.20 linux-2.4.20/arch/ia64/lib/ip_fast_csum.S

• Lines: 91
• Date: Thu Nov 28 15:53:09 2002
• Orig file: linux-2.4.19/arch/ia64/lib/ip_fast_csum.S
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/arch/ia64/lib/ip_fast_csum.S linux-2.4.20/arch/ia64/lib/ip_fast_csum.S
@@ -0,0 +1,90 @@
+/*
+ * Optmized version of the ip_fast_csum() function
+ * Used for calculating IP header checksum
+ *
+ * Return: 16bit checksum, complemented
+ *
+ * Inputs:
+ *      in0: address of buffer to checksum (char *)
+ *      in1: length of the buffer (int)
+ *
+ * Copyright (C) 2002 Intel Corp.
+ * Copyright (C) 2002 Ken Chen <kenneth.w.chen@intel.com>
+ */
+
+#include <asm/asmmacro.h>
+
+/*
+ * Since we know that most likely this function is called with buf aligned
+ * on 4-byte boundary and 20 bytes in length, we can execution rather quickly
+ * versus calling generic version of do_csum, which has lots of overhead in
+ * handling various alignments and sizes.  However, due to lack of constrains
+ * put on the function input argument, cases with alignment not on 4-byte or
+ * size not equal to 20 bytes will be handled by the generic do_csum function.
+ */
+
+#define in0	r32
+#define in1	r33
+#define ret0	r8
+
+GLOBAL_ENTRY(ip_fast_csum)
+	.prologue
+	.body
+	cmp.ne	p6,p7=5,in1	// size other than 20 byte?
+	and	r14=3,in0	// is it aligned on 4-byte?
+	add	r15=4,in0	// second source pointer
+	;;
+	cmp.ne.or.andcm p6,p7=r14,r0
+	;;
+(p7)	ld4	r20=[in0],8
+(p7)	ld4	r21=[r15],8
+(p6)	br.spnt	.generic
+	;;
+	ld4	r22=[in0],8
+	ld4	r23=[r15],8
+	;;
+	ld4	r24=[in0]
+	add	r20=r20,r21
+	add	r22=r22,r23
+	;;
+	add	r20=r20,r22
+	;;
+	add	r20=r20,r24
+	;;
+	shr.u	ret0=r20,16	// now need to add the carry
+	zxt2	r20=r20
+	;;
+	add	r20=ret0,r20
+	;;
+	shr.u	ret0=r20,16	// add carry again
+	zxt2	r20=r20
+	;;
+	add	r20=ret0,r20
+	;;
+	shr.u	ret0=r20,16
+	zxt2	r20=r20
+	;;
+	add	r20=ret0,r20
+	;;
+	andcm	ret0=-1,r20
+	.restore sp		// reset frame state
+	br.ret.sptk.many b0
+	;;
+
+.generic:
+	.prologue
+	.save ar.pfs, r35
+	alloc	r35=ar.pfs,2,2,2,0
+	.save rp, r34
+	mov	r34=b0
+	.body
+	dep.z	out1=in1,2,30
+	mov	out0=in0
+	;;
+	br.call.sptk.many b0=do_csum
+	;;
+	andcm	ret0=-1,ret0
+	mov	ar.pfs=r35
+	mov	b0=r34
+	br.ret.sptk.many b0
+END(ip_fast_csum)