Module Name: src
Committed By: matt
Date: Wed Jan 16 21:48:56 UTC 2013
Modified Files:
src/common/lib/libc/arch/arm/gen: byte_swap_4.S
Log Message:
Add some comments to illustrate what is actually happening.
To generate a diff of this commit:
cvs rdiff -u -r1.5 -r1.6 src/common/lib/libc/arch/arm/gen/byte_swap_4.S
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/common/lib/libc/arch/arm/gen/byte_swap_4.S
diff -u src/common/lib/libc/arch/arm/gen/byte_swap_4.S:1.5 src/common/lib/libc/arch/arm/gen/byte_swap_4.S:1.6
--- src/common/lib/libc/arch/arm/gen/byte_swap_4.S:1.5 Tue Nov 27 23:57:07 2012
+++ src/common/lib/libc/arch/arm/gen/byte_swap_4.S Wed Jan 16 21:48:56 2013
@@ -1,4 +1,4 @@
-/* $NetBSD: byte_swap_4.S,v 1.5 2012/11/27 23:57:07 matt Exp $ */
+/* $NetBSD: byte_swap_4.S,v 1.6 2013/01/16 21:48:56 matt Exp $ */
/*-
* Copyright (c) 1997 The NetBSD Foundation, Inc.
@@ -42,11 +42,11 @@ _ENTRY(_C_LABEL(htonl))
#endif
_PROF_PROLOGUE
#ifdef _ARM_ARCH_6
- rev r0, r0
+ rev r0, r0
#else
- eor r1, r0, r0, ror #16
- bic r1, r1, #0x00FF0000
- mov r0, r0, ror #8
- eor r0, r0, r1, lsr #8
+ eor r1, r0, r0, ror #16 /* 4.3.2.1 -> 42.31.42.31 */
+ bic r1, r1, #0x00FF0000 /* 42.31.42.31 -> 42.0.42.31 */
+ mov r0, r0, ror #8 /* 4.3.2.1 -> 1.4.3.2 */
+ eor r0, r0, r1, lsr #8 /* 1.4.3.2 ^ 0.42.0.42 -> 1.2.3.4 */
#endif
RET
