- Added a directory to hold contributed code which has not been integrated

with the library yet.

- The byteswap code was contributed by Peter Bengtsson. Thank you very much!


git-svn-id: file:///Users/olsen/Code/migration-svn-zu-git/logical-line-staging/clib2/trunk@15163 87f5fb63-7c3d-0410-a384-fd976d0f7a62

library/contrib/byteswap/byteswap_swab32.c

@@ -0,0 +1,112 @@
+
+#if defined(__GNUC__) && defined(__PPC__)
+
+/* r3=from, r4=to, r5=len, r6=index, r7=load/store temp */
+
+asm("\
+	.text\n\
+	.align 2\n\
+	.globl swab32\n\
+	.type swab32,@function\n\
+swab32:\n\
+	srawi.	%r5,%r5,2\n\
+	li			%r6,0\n\
+	bc			4,gt,.exit\n\
+	mtctr		%r5\n\
+.loop:\n\
+	lwbrx		%r7,%r6,%r3\n\
+	stwx		%r7,%r6,%r4\n\
+	addi		%r6,%r6,4\n\
+	bc			0,lt,.loop\n\
+.exit:\n\
+	or			%r3,%r4,%r4\n\
+	blr\n\
+");
+
+/* r3=from, r4=to, r5=len/temp, r6=index, r7=load/store temp, r8=cache hint
+ *
+ * The unrolled, cache-hinting version appears to be about 4.5% faster, but
+ * in this case I opted for the smaller implementation. swab64() appears to
+ * gain more from cache-hinting - probably because of it using more registers
+ * for intermediate storage.
+asm("\
+	.text\n\
+	.align 2\n\
+	.globl swab32\n\
+	.type swab32,@function\n\
+swab32:\n\
+	dcbt		0,%r3\n\
+	andi.		%r8,%r5,31		# The number of bytes handled in '.pre'. Used for prefetch hint.\n\
+	srawi		%r5,%r5,2		# Convert bytes-># of 32-bit words\n\
+	andi.		%r7,%r5,7\n\
+	li			%r6,0\n\
+	bc			4,gt,.preploop\n\
+	mtctr		%r7\n\
+.pre:								# One 32-bit word at a time until we have (nLeft%8)==0 \n\
+	lwbrx		%r7,%r6,%r3\n\
+	stwx		%r7,%r6,%r4\n\
+	addi		%r6,%r6,4\n\
+	bc			0,lt,.pre\n\
+.preploop:\n\
+	srawi.	%r5,%r5,3		# Divide by 8 again to get number of loops.\n\
+	addi		%r8,%r8,32		# Start address for next loop (from r3).\n\
+	bc			4,gt,.exit\n\
+	mtctr		%r5\n\
+.loop:							# Loop unrolled 8 times = 32 bytes = 1 cache-line (except on the 970).\n\
+	dcbt		%r8,%r3			# Cache hint (prefetch) for the next loop\n\
+	lwbrx		%r7,%r6,%r3\n\
+	stwx		%r7,%r6,%r4\n\
+	addi		%r6,%r6,4\n\
+	lwbrx		%r7,%r6,%r3\n\
+	stwx		%r7,%r6,%r4\n\
+	addi		%r6,%r6,4\n\
+	lwbrx		%r7,%r6,%r3\n\
+	stwx		%r7,%r6,%r4\n\
+	addi		%r6,%r6,4\n\
+	lwbrx		%r7,%r6,%r3\n\
+	stwx		%r7,%r6,%r4\n\
+	addi		%r6,%r6,4\n\
+	lwbrx		%r7,%r6,%r3\n\
+	stwx		%r7,%r6,%r4\n\
+	addi		%r6,%r6,4\n\
+	lwbrx		%r7,%r6,%r3\n\
+	stwx		%r7,%r6,%r4\n\
+	addi		%r6,%r6,4\n\
+	lwbrx		%r7,%r6,%r3\n\
+	stwx		%r7,%r6,%r4\n\
+	addi		%r6,%r6,4\n\
+	lwbrx		%r7,%r6,%r3\n\
+	stwx		%r7,%r6,%r4\n\
+	addi		%r6,%r6,4\n\
+	addi		%r8,%r8,32		# Update cache-hint offset\n\
+	bc			0,lt,.loop\n\
+.exit:\n\
+	or			%r3,%r4,%r4\n\
+	blr\n\
+");
+*/
+
+#else
+
+#include <sys/types.h>
+#include <stdint.h>
+
+void *swab32(void *from,void *to,ssize_t len)
+{
+int i;
+uint32_t *u32in=from,*u32out=to,tmp;
+
+for(i=0;i<(len>>2);i++) {
+	tmp=u32in[i];
+	u32out[i]=((tmp&0xff)<<24)|
+		((tmp&0xff00)<<8)|
+		((tmp&0xff0000)>>8)|
+		((tmp&0xff000000)>>24);
+}
+
+return(to);
+}
+
+#endif
+
+