symm/rijndael-arm-crypto.S (rijndael_setup_arm_crypto): Avoid reload.

Juggle the register allocation in the loop which copies over the first
key-data cycle, so as to arrange to leave the last copied key word in
r4.  Then we can elide the explicit load of r4 at the start of the main
key expansion loop, because it already has the right value, saving a
whole instruction.

diff --git a/symm/rijndael-arm-crypto.S b/symm/rijndael-arm-crypto.S
index 3014710655a3553423d9d1fef63c6e1d104c7974..b277bf78fa1d9b511eaf822667cdd39a011d36de 100644 (file)
--- a/symm/rijndael-arm-crypto.S
+++ b/symm/rijndael-arm-crypto.S
@@ -78,31 +78,30 @@ FUNC(rijndael_setup_arm_crypto)
        // sort this out.
        add     r9, r0, #w
        mov     r14, r3
-       ands    r4, r2, #3
+       ands    r6, r2, #3
        beq     1f
-       mov     r4, r4, lsl #3
-       rsb     r5, r4, #32
+       mov     r6, r6, lsl #3
+       rsb     r7, r6, #32
        bic     r2, r2, #3
-       ldr     r6, [r2], #4
+       ldr     r4, [r2], #4
 
-0:     ldr     r7, [r2], #4
-       mov     r6, r6, lsr r4
-       orr     r6, r7, lsl r5
-       str     r6, [r9], #4
-       mov     r6, r7
+0:     ldr     r5, [r2], #4
+       mov     r4, r4, lsr r6
+       orr     r4, r5, lsl r7
+       str     r4, [r9], #4
        subs    r14, r14, #1
+       movhi   r4, r5
        bhi     0b
        b       9f
 
-1:     ldr     r6, [r2], #4
-       str     r6, [r9], #4
+1:     ldr     r4, [r2], #4
+       str     r4, [r9], #4
        subs    r14, r14, #1
        bhi     1b
 
        // Find out other useful things and prepare for the main loop.
 9:     ldr     r7, [r0, #nr]           // number of rounds
        mla     r2, r1, r7, r1          // total key size in words
-       ldr     r4, [r9, #-4]           // most recent key word
        leaextq r5, rijndael_rcon       // round constants
        sub     r8, r2, r3              // minus what we've copied already
        veor    q1, q1                  // all-zero register for the key