[src/trunk]: src/sys/arch/arm/arm Add ldrd support (one additional instructio...

[matt <matt%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/41cd1a31685c
branches:  trunk
changeset: 783392:41cd1a31685c
user:      matt <matt%NetBSD.org@localhost>
date:      Tue Dec 18 14:08:25 2012 +0000

description:
Add ldrd support (one additional instruction over 5 ldrs) but two of them
won't be executed resulting in 2 less loads which should save a few cyles.

diffstat:

 sys/arch/arm/arm/cpu_in_cksum_v4hdr.S |  24 ++++++++++++++++++------
 1 files changed, 18 insertions(+), 6 deletions(-)

diffs (48 lines):

diff -r 93336e7cf975 -r 41cd1a31685c sys/arch/arm/arm/cpu_in_cksum_v4hdr.S
--- a/sys/arch/arm/arm/cpu_in_cksum_v4hdr.S     Tue Dec 18 13:41:42 2012 +0000
+++ b/sys/arch/arm/arm/cpu_in_cksum_v4hdr.S     Tue Dec 18 14:08:25 2012 +0000
@@ -29,18 +29,30 @@
 
 #include <machine/asm.h>
 
-RCSID("$NetBSD: cpu_in_cksum_v4hdr.S,v 1.1 2012/12/18 13:41:42 matt Exp $")
+RCSID("$NetBSD: cpu_in_cksum_v4hdr.S,v 1.2 2012/12/18 14:08:25 matt Exp $")
 
 ENTRY(cpu_in_cksum_v4hdr)
+#ifdef _ARM_ARCH_DWORD_OK
+       tst     r0, #4                  /* 64-bit aligned? */
+       ldreqd  r2, [r0], #8            /* load 1st/2nd words */
+       ldrne   ip, [r0], #4            /* load 1st word */
+       ldreq   ip, [r0, #8]            /* load 5th word */
+       ldrned  r2, [r0, #8]            /* load 4th/5th words */
+#else
        ldr     ip, [r0]                /* load 1st word */
        ldr     r3, [r0, #4]            /* load 2nd word */
-       adds    r3, r3, ip              /* add 1st to 2nd */
        ldr     r2, [r0, #8]            /* load 3rd word */
-       adcs    r2, r2, r3              /* add sum to 3rd */
+#endif
+       adds    r3, r3, ip              /* accumulate */
+       adcs    r2, r2, r3              /* accumulate */
+#ifdef _ARM_ARCH_DWORD_OK
+       ldrd    r0, [r0]                /* load remaining words */
+#else
        ldr     r1, [r0, #12]           /* load 4th word */
-       adcs    r1, r1, r2              /* add sum to 4th */
        ldr     r0, [r0, #16]           /* load 5th word */
-       adcs    r0, r0, r1              /* add sum to 5th */
+#endif
+       adcs    r1, r1, r2              /* accumulate */
+       adcs    r0, r0, r1              /* accumulate */
        /*
         * We now have a 33-bit (r0 + carry) sum which needs to resolved to a
         * 16-bit sum.
@@ -62,7 +74,7 @@
        movw    r1, #0xffff             /* load 0xffff */
 #else
        mov     r1, #0x10000            /* load 0x10000 */
-       sub     r1, r1, #1              /* subtract 1 to get 0xffff */
+       sub     r1, r1, #1              /* subtract by 1 to get 0xffff */
 #endif
        subge   r0, r0, r1              /* subtract 0xffff */
        eor     r0, r0, r1              /* complement lower halfword */