| /* Copyright lowRISC contributors. */ |
| /* Licensed under the Apache License, Version 2.0, see LICENSE for details. */ |
| /* SPDX-License-Identifier: Apache-2.0 */ |
| /* |
| An example of how hardware loops work in OTBN |
| */ |
| .section .text.start |
| |
| /* The basic loop instruction (running 2 instructions 3 times) */ |
| li x2, 3 |
| li x3, 0 |
| |
| loop x2, 2 |
| addi x3, x3, 2 |
| addi x3, x3, -1 |
| |
| /* At this point, we've incremented x3 by 2-1 = 1 on each of three |
| loop iterations, so x3 should equal 3. */ |
| |
| loopi 5, 1 |
| addi x3, x3, -3 |
| |
| /* Now we've run a loop that decrements x3 by 3 on each of |
| five loop iterations, so it should now equal 3-15 = -12. */ |
| |
| loop x2, 3 |
| loopi 4, 1 |
| addi x3, x3, 2 |
| nop |
| |
| /* The nested loop runs 3 * 4 times, incrementing by 2 each |
| iteration. So x3 should now equal -12 + 2*12 = 12. */ |
| |
| ecall |
