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@ Written by Wilco Dijkstra, 1996. Refer to file LICENSE under
@ trunk/third_party_mods/sqrt_floor.
@
@ Minor modifications in code style for WebRTC, 2012.
@ Output is bit-exact with the reference C code in spl_sqrt_floor.c.
@ Input : r0 32 bit unsigned integer
@ Output: r0 = INT (SQRT (r0)), precision is 16 bits
@ Registers touched: r1, r2
.global WebRtcSpl_SqrtFloor
.align 2
WebRtcSpl_SqrtFloor:
mov r1, #3 << 30
mov r2, #1 << 30
@ unroll for i = 0 .. 15
cmp r0, r2, ror #2 * 0
subhs r0, r0, r2, ror #2 * 0
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 1
subhs r0, r0, r2, ror #2 * 1
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 2
subhs r0, r0, r2, ror #2 * 2
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 3
subhs r0, r0, r2, ror #2 * 3
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 4
subhs r0, r0, r2, ror #2 * 4
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 5
subhs r0, r0, r2, ror #2 * 5
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 6
subhs r0, r0, r2, ror #2 * 6
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 7
subhs r0, r0, r2, ror #2 * 7
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 8
subhs r0, r0, r2, ror #2 * 8
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 9
subhs r0, r0, r2, ror #2 * 9
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 10
subhs r0, r0, r2, ror #2 * 10
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 11
subhs r0, r0, r2, ror #2 * 11
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 12
subhs r0, r0, r2, ror #2 * 12
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 13
subhs r0, r0, r2, ror #2 * 13
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 14
subhs r0, r0, r2, ror #2 * 14
adc r2, r1, r2, lsl #1
cmp r0, r2, ror #2 * 15
subhs r0, r0, r2, ror #2 * 15
adc r2, r1, r2, lsl #1
bic r0, r2, #3 << 30 @ for rounding add: cmp r0, r2 adc r2, #1
bx lr
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