[opt] [bug] Simplify modulo POT (Stage 2)

[xumingkuan]

Related issue = #944
A continuation of #2352 and fixes a bug introduced in that PR.

Test case:

import taichi as ti

ti.init(print_ir=True)


@ti.kernel
def func(i: ti.u32):
    if i % 2 == 1:
        print(i)


func(1)

Before:

    <i32> $1 = const [1]
    <u32> $2 = arg[0]
    <u32> $3 = const [1]
    <u32> $4 = bit_and $2 $3
    <u32> $5 = sub $2 $4
    <i32> $6 = cmp_eq $5 $3
    <i32> $7 = bit_and $6 $1
    $8 : if $7 {
      print $2, "\n"
    }

After:

    <i32> $1 = const [1]
    <u32> $2 = arg[0]
    <u32> $3 = const [1]
    <u32> $4 = bit_and $2 $3
    <i32> $5 = cmp_eq $4 $3
    <i32> $6 = bit_and $5 $1
    $7 : if $6 {
      print $2, "\n"
    }

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[k-ye]

Please add the test if there was a bug, thx!

[k-ye]

Thanks LGTM!