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optimize decode_bit some more -> 166b

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Dennis Ranke
2022-09-18 23:11:26 +02:00
parent 612084a5bf
commit 5c7aee046a
1 changed files with 14 additions and 17 deletions
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31
asm_unpackers/unpack_armv6m.S
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@@ -111,47 +111,44 @@ upkr_decode_length:
.type upkr_decode_bit, %function
// r0 .. tmp / prob (saved)
// r1 .. out_ptr (modified)
// r1 .. in_ptr (modified)
// r2 .. state (modified)
// r3 .. scratch (saved)
// r4 ..
// r5 .. context index (preserved)
// r6 .. bit (returned)
// r7 .. probs ptr (preserved)
upkr_decode_bit:
push { r0, r3, lr }
.Lstate_loop:
lsrs r3, r2, #12
bne 1f
upkr_fill_state:
lsls r2, r2, #8
ldrb r6, [r1]
adds r1, r1, #1
orrs r2, r2, r6
b .Lstate_loop
1:
upkr_decode_bit:
lsrs r6, r2, #12
beq upkr_fill_state
push { r0, r1, r3, lr }
ldrb r0, [r7, r5]
lsrs r3, r2, #8
uxtb r2, r2
uxtb r1, r2
subs r6, r2, r0
subs r6, r1, r0
blt 1f
subs r2, r2, r0
subs r1, r2, r0
rsbs r0, r0, #0
uxtb r0, r0
1:
muls r3, r3, r0
adds r2, r2, r3
adds r2, r1, r3
rsbs r3, r0, #0
uxtb r3, r3
adds r3, r3, #8
lsrs r3, r3, #4
adds r0, r0, r3
adcs r0, r0, r3
cmp r6, #0
blt 1f
@@ -162,4 +159,4 @@ upkr_decode_bit:
strb r0, [r7, r5]
lsrs r6, r6, #31
pop { r0, r3, pc }
pop { r0, r1, r3, pc }