Zir: make src_node of type declarations non-optional

Previously, the `src_node` field of `struct_decl`, `union_decl`,
`enum_decl`, and `opaque_decl` was optional, included in trailing data
only if a flag in `Small` was set. However, this was unnecessary logic:
AstGen always provided the source node. We can simplify a few bits of
logic by making this field non-optional, moving it into non-trailing
data.

There was one place where the field was actually omitted before: the
root struct of a file was at source node 0, so the node was
coincidentally elided. Therefore, this commit has a fixed cost of 4
bytes of ZIR per file.

1 files changed, 10 insertions, 27 deletions

diff --git a/src/Sema.zig b/src/Sema.zig
index 3465f923a8..45f0edcb56 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -2725,7 +2725,6 @@ pub fn getStructType(
     const small: Zir.Inst.StructDecl.Small = @bitCast(extended.small);
 
     var extra_index: usize = extended.operand + @typeInfo(Zir.Inst.StructDecl).Struct.fields.len;
-    extra_index += @intFromBool(small.has_src_node);
     const fields_len = if (small.has_fields_len) blk: {
         const fields_len = sema.code.extra[extra_index];
         extra_index += 1;
@@ -2778,10 +2777,7 @@ fn zirStructDecl(
     const mod = sema.mod;
     const ip = &mod.intern_pool;
     const small: Zir.Inst.StructDecl.Small = @bitCast(extended.small);
-    const src: LazySrcLoc = if (small.has_src_node) blk: {
-        const node_offset: i32 = @bitCast(sema.code.extra[extended.operand + @typeInfo(Zir.Inst.StructDecl).Struct.fields.len]);
-        break :blk LazySrcLoc.nodeOffset(node_offset);
-    } else unreachable; // MLUGG TODO
+    const src = sema.code.extraData(Zir.Inst.StructDecl, extended.operand).data.src();
 
     // Because these three things each reference each other, `undefined`
     // placeholders are used before being set after the struct type gains an
@@ -2941,13 +2937,10 @@ fn zirEnumDecl(
     const mod = sema.mod;
     const gpa = sema.gpa;
     const small: Zir.Inst.EnumDecl.Small = @bitCast(extended.small);
-    var extra_index: usize = extended.operand + @typeInfo(Zir.Inst.EnumDecl).Struct.fields.len;
+    const extra = sema.code.extraData(Zir.Inst.EnumDecl, extended.operand);
+    var extra_index: usize = extra.end;
 
-    const src: LazySrcLoc = if (small.has_src_node) blk: {
-        const node_offset: i32 = @bitCast(sema.code.extra[extra_index]);
-        extra_index += 1;
-        break :blk LazySrcLoc.nodeOffset(node_offset);
-    } else unreachable; // MLUGG TODO
+    const src = extra.data.src();
     const tag_ty_src: LazySrcLoc = .{ .node_offset_container_tag = src.node_offset.x };
 
     const tag_type_ref = if (small.has_tag_type) blk: {
@@ -3214,13 +3207,10 @@ fn zirUnionDecl(
     const mod = sema.mod;
     const gpa = sema.gpa;
     const small: Zir.Inst.UnionDecl.Small = @bitCast(extended.small);
-    var extra_index: usize = extended.operand + @typeInfo(Zir.Inst.UnionDecl).Struct.fields.len;
+    const extra = sema.code.extraData(Zir.Inst.UnionDecl, extended.operand);
+    var extra_index: usize = extra.end;
 
-    const src: LazySrcLoc = if (small.has_src_node) blk: {
-        const node_offset: i32 = @bitCast(sema.code.extra[extra_index]);
-        extra_index += 1;
-        break :blk LazySrcLoc.nodeOffset(node_offset);
-    } else unreachable; // MLUGG TODO
+    const src = extra.data.src();
 
     extra_index += @intFromBool(small.has_tag_type);
     extra_index += @intFromBool(small.has_body_len);
@@ -3323,13 +3313,10 @@ fn zirOpaqueDecl(
 
     const mod = sema.mod;
     const small: Zir.Inst.OpaqueDecl.Small = @bitCast(extended.small);
-    var extra_index: usize = extended.operand;
+    const extra = sema.code.extraData(Zir.Inst.OpaqueDecl, extended.operand);
+    var extra_index: usize = extra.end;
 
-    const src: LazySrcLoc = if (small.has_src_node) blk: {
-        const node_offset: i32 = @bitCast(sema.code.extra[extra_index]);
-        extra_index += 1;
-        break :blk LazySrcLoc.nodeOffset(node_offset);
-    } else unreachable; // MLUGG TODO
+    const src = extra.data.src();
 
     const decls_len = if (small.has_decls_len) blk: {
         const decls_len = sema.code.extra[extra_index];
@@ -35662,7 +35649,6 @@ fn semaBackingIntType(mod: *Module, struct_type: InternPool.Key.StructType) Comp
 
     if (small.has_backing_int) {
         var extra_index: usize = extended.operand + @typeInfo(Zir.Inst.StructDecl).Struct.fields.len;
-        extra_index += @intFromBool(small.has_src_node);
         extra_index += @intFromBool(small.has_fields_len);
         extra_index += @intFromBool(small.has_decls_len);
 
@@ -36374,8 +36360,6 @@ fn structZirInfo(zir: Zir, zir_index: Zir.Inst.Index) struct {
     const small: Zir.Inst.StructDecl.Small = @bitCast(extended.small);
     var extra_index: usize = extended.operand + @typeInfo(Zir.Inst.StructDecl).Struct.fields.len;
 
-    extra_index += @intFromBool(small.has_src_node);
-
     const fields_len = if (small.has_fields_len) blk: {
         const fields_len = zir.extra[extra_index];
         extra_index += 1;
@@ -36843,7 +36827,6 @@ fn semaUnionFields(mod: *Module, arena: Allocator, union_type: InternPool.Key.Un
     var extra_index: usize = extended.operand + @typeInfo(Zir.Inst.UnionDecl).Struct.fields.len;
 
     const src = LazySrcLoc.nodeOffset(0);
-    extra_index += @intFromBool(small.has_src_node);
 
     const tag_type_ref: Zir.Inst.Ref = if (small.has_tag_type) blk: {
         const ty_ref: Zir.Inst.Ref = @enumFromInt(zir.extra[extra_index]);