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Date: Tue, 3 Sep 2013 00:57:56 +0100
From: Rafael Waldo Delgado Doblas <lord.rafa@...il.com>
To: john-dev@...ts.openwall.com
Subject: Rafael's weekly report #12
Hello,
Accomplishments:
1. Debuged epiphany-scrypt and driver-epiphany.
2. Replaced memcpy, it improve a little bit the performance.
3. Started with asm inline codification.
Priorities:
1. Follow with asm codification,
Well I started with inline asm. But the results weren’t better than C. This
is because the C compiler optimizes the Bout vector access storing it in
the general registers and after calls to R macro:
7b0: 879f e10a add r60,r1,r23
7b4: b32f fc06 lsr r61,r60,0x19
7b8: 90ff fc06 lsl r60,r60,0x7
7bc: 967f ff8a orr r60,r61,r60
7c0: 4a0f 6f8a eor r26,r26,r60
Howerver when I define the R function with inline asm:
__asm__("LSR r60, %1, %3\n\tIMADD r60, %1, %4\n\t EOR %0, %1, r60" \
: "=r"(b)\
: "r"(a), "r"(b), "n"(c), "r"(d) \
: "memory", "%r60" \
);
This optimization is not performed, this adds 2 instructions more:
788: 4a4c c001 ldr r50,[r2,+0xc]
78c: 284c c000 ldr r49,[r2,+0x0]
790: 289f db0a add r49,r50,r49
794: 84ef f806 lsr r60,r49,0x7
798: 863f f887 fmadd r60,r49,r12
79c: 260f db8a eor r49,r49,r60
7a0: 2a5c c000 str r49,[r2,+0x4]
BTW fmadd/imadd has cannot work with immediate values then we will need to
add extra 4 movs in order to store the multiplication constants in
registers.
I will write a new ASM file with the salsa20_8 implementation using the C
optimized version as base.
Regards,
Rafael.
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