// on the tour from p1 to p2.  We've precomputed minimum
	// depth blocks for powers-of-two subsequences of the tour.
	// Combine the right two precomputed values to get the answer.
	logS := uint(log64(int64(p2 - p1)))
	bid1 := lca.rangeMin[logS][p1]
	bid2 := lca.rangeMin[logS][p2-1<<logS+1]
	if lca.blocks[bid1].depth < lca.blocks[bid2].depth {
		return lca.blocks[bid1].b
	}
	return lca.blocks[bid2].b

((NE|EQ) (TESTQconst [c] x)) && isUint64PowerOfTwo(int64(c))
    => ((ULT|UGE) (BTQconst [int8(log32(c))] x))
((NE|EQ) (TESTQ (MOVQconst [c]) x)) && isUint64PowerOfTwo(c)
    => ((ULT|UGE) (BTQconst [int8(log64(c))] x))
(SET(NE|EQ) (TESTL (SHLL (MOVLconst [1]) x) y)) => (SET(B|AE)  (BTL x y))
(SET(NE|EQ) (TESTQ (SHLQ (MOVQconst [1]) x) y)) => (SET(B|AE)  (BTQ x y))
(SET(NE|EQ) (TESTLconst [c] x)) && isUint32PowerOfTwo(int64(c))

(MULV _ (MOVVconst [0])) => (MOVVconst [0])
(MULV x (MOVVconst [1])) => x
(MULV x (MOVVconst [c])) && isPowerOfTwo64(c) => (SLLVconst [log64(c)] x)

// div by constant
(DIVVU x (MOVVconst [1])) => x
(DIVVU x (MOVVconst [c])) && isPowerOfTwo64(c) => (SRLVconst [log64(c)] x)
(REMVU _ (MOVVconst [1])) => (MOVVconst [0])                       // mod
(REMVU x (MOVVconst [c])) && isPowerOfTwo64(c) => (ANDconst [c-1] x) // mod

(Div64 <t> n (Const64 [c])) && isPowerOfTwo64(c) =>
  (Rsh64x64
    (Add64 <t> n (Rsh64Ux64 <t> (Rsh64x64 <t> n (Const64 <typ.UInt64> [63])) (Const64 <typ.UInt64> [int64(64-log64(c))])))
    (Const64 <typ.UInt64> [int64(log64(c))]))

// Signed divide, not a power of 2.  Strength reduce to a multiply.
(Div8 <t> x (Const8 [c])) && smagicOK8(c) =>
  (Sub8 <t>
    (Rsh32x64 <t>
      (Mul32 <typ.UInt32>

(Select1 (MULVU x (MOVVconst [1]))) => x
(Select1 (MULVU x (MOVVconst [c]))) && isPowerOfTwo64(c) => (SLLVconst [log64(c)] x)

// div by constant
(Select1 (DIVVU x (MOVVconst [1]))) => x
(Select1 (DIVVU x (MOVVconst [c]))) && isPowerOfTwo64(c) => (SRLVconst [log64(c)] x)
(Select0 (DIVVU _ (MOVVconst [1]))) => (MOVVconst [0])                       // mod

	// result: (BTRQconst [int8(log64(^c))] x)
	for {
		for _i0 := 0; _i0 <= 1; _i0, v_0, v_1 = _i0+1, v_1, v_0 {
			if v_0.Op != OpAMD64MOVQconst {
				continue
			}
			c := auxIntToInt64(v_0.AuxInt)
			x := v_1
			if !(isUint64PowerOfTwo(^c) && uint64(^c) >= 1<<31) {
				continue
			}
			v.reset(OpAMD64BTRQconst)
			v.AuxInt = int8ToAuxInt(int8(log64(^c)))
			v.AddArg(x)
			return true

	// match: (DIVVU x (MOVVconst [c]))
	// cond: isPowerOfTwo64(c)
	// result: (SRLVconst [log64(c)] x)
	for {
		x := v_0
		if v_1.Op != OpLOONG64MOVVconst {
			break
		}
		c := auxIntToInt64(v_1.AuxInt)
		if !(isPowerOfTwo64(c)) {
			break
		}
		v.reset(OpLOONG64SRLVconst)
		v.AuxInt = int64ToAuxInt(log64(c))
		v.AddArg(x)
		return true
	}

				continue
			}
			v.copyOf(x)
			return true
		}
		break
	}
	// match: (Select1 (MULVU x (MOVVconst [c])))
	// cond: isPowerOfTwo64(c)
	// result: (SLLVconst [log64(c)] x)
	for {
		if v_0.Op != OpMIPS64MULVU {
			break
		}
		_ = v_0.Args[1]
		v_0_0 := v_0.Args[0]
		v_0_1 := v_0.Args[1]
		for _i0 := 0; _i0 <= 1; _i0, v_0_0, v_0_1 = _i0+1, v_0_1, v_0_0 {

	return int64(bits.Len8(uint8(n))) - 1
}
func log16(n int16) int64 {
	return int64(bits.Len16(uint16(n))) - 1
}
func log32(n int32) int64 {
	return int64(bits.Len32(uint32(n))) - 1
}
func log64(n int64) int64 {
	return int64(bits.Len64(uint64(n))) - 1
}

// log2uint32 returns logarithm in base 2 of uint32(n), with log2(0) = -1.
// Rounds down.
func log2uint32(n int64) int64 {

	// result: (Rsh64Ux64 n (Const64 <typ.UInt64> [log64(c)]))
	for {
		n := v_0
		if v_1.Op != OpConst64 {
			break
		}
		c := auxIntToInt64(v_1.AuxInt)
		if !(isNonNegative(n) && isPowerOfTwo64(c)) {
			break
		}
		v.reset(OpRsh64Ux64)
		v0 := b.NewValue0(v.Pos, OpConst64, typ.UInt64)
		v0.AuxInt = int64ToAuxInt(log64(c))
		v.AddArg2(n, v0)
		return true
	}