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Add integer power functions #212

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Merged
merged 12 commits into from
Sep 9, 2018
Merged

Add integer power functions #212

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372062c
init (WIP)
MaxGraey Aug 5, 2018
f2b4833
refactor
MaxGraey Aug 5, 2018
95be0cf
update (wip)
MaxGraey Aug 5, 2018
16c4a7f
remove redundance code for speedup
MaxGraey Aug 5, 2018
9e1c862
use shorter name for identifiers
MaxGraey Aug 5, 2018
c32bcd2
early reject overflowed results
MaxGraey Aug 5, 2018
6fe1e80
update. Make two versions ipow32 & ipow64
MaxGraey Aug 5, 2018
8436ff5
minor refactoring
MaxGraey Aug 6, 2018
d03cbc2
add tests for ipow64
MaxGraey Aug 6, 2018
d913de7
handle overflow with big exponents and optimaze for shinkage >= 1
MaxGraey Aug 6, 2018
7875b45
better code compation
MaxGraey Aug 6, 2018
4b9527f
add special test
MaxGraey Aug 7, 2018
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108 changes: 108 additions & 0 deletions std/assembly/math.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2303,3 +2303,111 @@ export namespace NativeMathf {
return sx ? -x : x;
}
}

export function ipow32(x: i32, e: i32): i32 {
var out = 1;
if (ASC_SHRINK_LEVEL < 1) {
if (e < 0) return 0;

switch (e) {
case 0: return 1;
case 1: return x;
case 2: return x * x;
}

let log = 32 - clz(e);
if (log <= 5) {
// 32 = 2 ^ 5, so need only five cases.
// But some extra cases needs for properly overflowing
switch (log) {
case 5: {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
case 4: {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
case 3: {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
case 2: {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
case 1: {
if (e & 1) out *= x;
}
}
return out;
}
}

while (e > 0) {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
return out;
}

export function ipow64(x: i64, e: i32): i64 {
var out: i64 = 1;
if (ASC_SHRINK_LEVEL < 1) {
if (e < 0) return 0;
switch (e) {
case 0: return 1;
case 1: return x;
case 2: return x * x;
}

let log = 32 - clz(e);
if (log <= 6) {
// 64 = 2 ^ 6, so need only six cases.
// But some extra cases needs for properly overflowing
switch (log) {
case 6: {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
case 5: {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
case 4: {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
case 3: {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
case 2: {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
case 1: {
if (e & 1) out *= x;
}
}
return out;
}
}

while (e > 0) {
if (e & 1) out *= x;
e >>= 1;
x *= x;
}
return out;
}
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