InternPool,Sema,type,llvm: alignment fixes

This changeset fixes the handling of alignment in several places. The
new rules are:
* `@alignOf(T)` where `T` is a runtime zero-bit type is at least 1,
  maybe greater.
* Zero-bit fields in `extern` structs *do* force alignment, potentially
  offsetting following fields.
* Zero-bit fields *do* have addresses within structs which can be
  observed and are consistent with `@offsetOf`.

These are not necessarily all implemented correctly yet (see disabled
test), but this commit fixes all regressions compared to master, and
makes one new test pass.

1 files changed, 7 insertions, 18 deletions

diff --git a/test/behavior/alignof.zig b/test/behavior/alignof.zig
index b414b7e056..0443b2d6b3 100644
--- a/test/behavior/alignof.zig
+++ b/test/behavior/alignof.zig
@@ -18,24 +18,13 @@ test "@alignOf(T) before referencing T" {
 }
 
 test "comparison of @alignOf(T) against zero" {
-    {
-        const T = struct { x: u32 };
-        try expect(!(@alignOf(T) == 0));
-        try expect(@alignOf(T) != 0);
-        try expect(!(@alignOf(T) < 0));
-        try expect(!(@alignOf(T) <= 0));
-        try expect(@alignOf(T) > 0);
-        try expect(@alignOf(T) >= 0);
-    }
-    {
-        const T = struct {};
-        try expect(@alignOf(T) == 0);
-        try expect(!(@alignOf(T) != 0));
-        try expect(!(@alignOf(T) < 0));
-        try expect(@alignOf(T) <= 0);
-        try expect(!(@alignOf(T) > 0));
-        try expect(@alignOf(T) >= 0);
-    }
+    const T = struct { x: u32 };
+    try expect(!(@alignOf(T) == 0));
+    try expect(@alignOf(T) != 0);
+    try expect(!(@alignOf(T) < 0));
+    try expect(!(@alignOf(T) <= 0));
+    try expect(@alignOf(T) > 0);
+    try expect(@alignOf(T) >= 0);
 }
 
 test "correct alignment for elements and slices of aligned array" {