Support bit fields in interop

Fix #728

backend.native/tests/interop/basics/bf.kt

@@ -0,0 +1,74 @@
+import bitfields.*
+import kotlinx.cinterop.*
+
+fun assertEquals(value1: Any?, value2: Any?) {
+    if (value1 != value2)
+        throw AssertionError("Expected $value1, got $value2")
+}
+
+fun check(s: S, x1: Long, x2: B2, x3: Short, x4: Int, x5: Int, x6: Long) {
+    assertEquals(x1, s.x1)
+    assertEquals(x1, getX1(s.ptr))
+
+    assertEquals(x2, s.x2)
+    assertEquals(x2, getX2(s.ptr))
+
+    assertEquals(x3, s.x3)
+    assertEquals(x3, getX3(s.ptr))
+
+    assertEquals(x4, s.x4)
+    assertEquals(x4, getX4(s.ptr))
+
+    assertEquals(x5, s.x5)
+    assertEquals(x5, getX5(s.ptr))
+
+    assertEquals(x6, s.x6)
+    assertEquals(x6, getX6(s.ptr))
+}
+
+fun assign(s: S, x1: Long, x2: B2, x3: Short, x4: Int, x5: Int, x6: Long) {
+    s.x1 = x1
+    s.x2 = x2
+    s.x3 = x3
+    s.x4 = x4
+    s.x5 = x5
+    s.x6 = x6
+}
+
+fun assignReversed(s: S, x1: Long, x2: B2, x3: Short, x4: Int, x5: Int, x6: Long) {
+    s.x6 = x6
+    s.x5 = x5
+    s.x4 = x4
+    s.x3 = x3
+    s.x2 = x2
+    s.x1 = x1
+}
+
+fun test(s: S, x1: Long, x2: B2, x3: Short, x4: Int, x5: Int, x6: Long) {
+    assign(s, x1, x2, x3, x4, x5, x6)
+    check(s, x1, x2, x3, x4, x5, x6)
+
+    assignReversed(s, x1, x2, x3, x4, x5, x6)
+    check(s, x1, x2, x3, x4, x5, x6)
+
+    // Also check with some insignificant bits modified:
+
+    assign(s, x1 + 2, x2, (x3 + 8).toShort(), x4 - 16, x5 + 32, x6 + Long.MIN_VALUE)
+    check(s, x1, x2, x3, x4, x5, x6)
+
+    assignReversed(s, x1 + 2, x2, (x3 + 8).toShort(), x4 - 16, x5 + 32, x6 + Long.MIN_VALUE)
+    check(s, x1, x2, x3, x4, x5, x6)
+}
+
+fun main(args: Array<String>) {
+    memScoped {
+        val s = alloc<S>()
+        for (x1 in -1L..0L)
+            for (x2 in B2.values())
+                for (x3 in 0..7)
+                    for (x4 in intArrayOf(0, 6, 15))
+                        for (x5 in intArrayOf(-16, -2, -1, 0, 5, 15))
+                            for (x6 in longArrayOf(Long.MIN_VALUE/2, -1L shl 36, -325L, 0, 1L shl 48, Long.MAX_VALUE/2))
+                                test(s, x1, x2, x3.toShort(), x4, x5, x6)
+    }
+}

backend.native/tests/interop/basics/bitfields.def

@@ -0,0 +1,20 @@
+---
+enum B2 {
+    ZERO, ONE, TWO, THREE
+};
+
+struct __attribute__((packed)) S {
+    long long x1 : 1;
+    enum B2 x2 : 2;
+    unsigned short x3 : 3;
+    unsigned int x4 : 4;
+    int x5 : 5;
+    long long x6 : 63;
+};
+
+static long long getX1(struct S* s) { return s->x1; }
+static enum B2 getX2(struct S* s) { return s->x2; }
+static unsigned short getX3(struct S* s) { return s->x3; }
+static unsigned int getX4(struct S* s) { return s->x4; }
+static int getX5(struct S* s) { return s->x5; }
+static long long getX6(struct S* s) { return s->x6; }