[JS IR] stdlib: port methods that use bit representation of numbers

- Port part of 'misc.js' from current backend to 'bitUtils.kt' in IR backend
- Enable toBits, toRawBits, fromBits extension function on Double and Float
- Enable Double.withSign
- Refactor getNumberHashCode using new utils

libraries/stdlib/js-ir/runtime/bitUtils.kt

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.js.internal
+
+private external class ArrayBuffer(size: Int)
+private external class Float64Array(buffer: ArrayBuffer)
+private external class Float32Array(buffer: ArrayBuffer)
+private external class Int32Array(buffer: ArrayBuffer)
+
+@PublishedApi
+internal object BitUtils {
+    private val buf = ArrayBuffer(8)
+    private val bufFloat64 = Float64Array(buf).unsafeCast<DoubleArray>()
+    private val bufFloat32 = Float32Array(buf).unsafeCast<FloatArray>()
+    private val bufInt32 = Int32Array(buf).unsafeCast<IntArray>()
+    private var lowIndex = 0
+    private var highIndex = 1
+
+    init {
+        bufFloat64[0] = -1.0  // bff00000_00000000
+        if (bufInt32[lowIndex] != 0) {
+            lowIndex = 1
+            highIndex = 0
+        }
+    }
+
+    fun doubleToRawBits(value: Double): Long {
+        bufFloat64[0] = value
+        return Long(bufInt32[lowIndex], bufInt32[highIndex])
+    }
+
+    fun doubleFromBits(value: Long): Double {
+        bufInt32[lowIndex] = value.low
+        bufInt32[highIndex] = value.high
+        return bufFloat64[0]
+    }
+
+    fun floatToRawBits(value: Float): Int {
+        bufFloat32[0] = value
+        return bufInt32[0]
+    }
+
+    fun floatFromBits(value: Int): Float {
+        bufInt32[0] = value
+        return bufFloat32[0]
+    }
+
+    // returns zero value for number with positive sign bit and non-zero value for number with negative sign bit.
+    fun doubleSignBit(value: Double): Int {
+        bufFloat64[0] = value
+        return bufInt32[highIndex] and Int.MIN_VALUE
+    }
+
+    fun getNumberHashCode(obj: Double): Int {
+        if (jsBitwiseOr(obj, 0).unsafeCast<Double>() === obj) {
+            return obj.toInt()
+        }
+
+        bufFloat64[0] = obj
+        return bufInt32[highIndex] * 31 + bufInt32[lowIndex]
+    }
+}