1 files changed, 163 insertions, 0 deletions
diff --git a/src/codegen/arm/abi.zig b/src/codegen/arm/abi.zig
new file mode 100644
index 0000000000..23606d6145
--- /dev/null
+++ b/src/codegen/arm/abi.zig
@@ -0,0 +1,163 @@
+const std = @import("std");
+const assert = std.debug.assert;
+const RegisterManagerFn = @import("../../register_manager.zig").RegisterManager;
+const Type = @import("../../Type.zig");
+const Zcu = @import("../../Zcu.zig");
+
+pub const Class = union(enum) {
+    memory,
+    byval,
+    i32_array: u8,
+    i64_array: u8,
+
+    fn arrSize(total_size: u64, arr_size: u64) Class {
+        const count = @as(u8, @intCast(std.mem.alignForward(u64, total_size, arr_size) / arr_size));
+        if (arr_size == 32) {
+            return .{ .i32_array = count };
+        } else {
+            return .{ .i64_array = count };
+        }
+    }
+};
+
+pub const Context = enum { ret, arg };
+
+pub fn classifyType(ty: Type, zcu: *Zcu, ctx: Context) Class {
+    assert(ty.hasRuntimeBitsIgnoreComptime(zcu));
+
+    var maybe_float_bits: ?u16 = null;
+    const max_byval_size = 512;
+    const ip = &zcu.intern_pool;
+    switch (ty.zigTypeTag(zcu)) {
+        .@"struct" => {
+            const bit_size = ty.bitSize(zcu);
+            if (ty.containerLayout(zcu) == .@"packed") {
+                if (bit_size > 64) return .memory;
+                return .byval;
+            }
+            if (bit_size > max_byval_size) return .memory;
+            const float_count = countFloats(ty, zcu, &maybe_float_bits);
+            if (float_count <= byval_float_count) return .byval;
+
+            const fields = ty.structFieldCount(zcu);
+            var i: u32 = 0;
+            while (i < fields) : (i += 1) {
+                const field_ty = ty.fieldType(i, zcu);
+                const field_alignment = ty.fieldAlignment(i, zcu);
+                const field_size = field_ty.bitSize(zcu);
+                if (field_size > 32 or field_alignment.compare(.gt, .@"32")) {
+                    return Class.arrSize(bit_size, 64);
+                }
+            }
+            return Class.arrSize(bit_size, 32);
+        },
+        .@"union" => {
+            const bit_size = ty.bitSize(zcu);
+            const union_obj = zcu.typeToUnion(ty).?;
+            if (union_obj.flagsUnordered(ip).layout == .@"packed") {
+                if (bit_size > 64) return .memory;
+                return .byval;
+            }
+            if (bit_size > max_byval_size) return .memory;
+            const float_count = countFloats(ty, zcu, &maybe_float_bits);
+            if (float_count <= byval_float_count) return .byval;
+
+            for (union_obj.field_types.get(ip), 0..) |field_ty, field_index| {
+                if (Type.fromInterned(field_ty).bitSize(zcu) > 32 or
+                    ty.fieldAlignment(field_index, zcu).compare(.gt, .@"32"))
+                {
+                    return Class.arrSize(bit_size, 64);
+                }
+            }
+            return Class.arrSize(bit_size, 32);
+        },
+        .bool, .float => return .byval,
+        .int => {
+            // TODO this is incorrect for _BitInt(128) but implementing
+            // this correctly makes implementing compiler-rt impossible.
+            // const bit_size = ty.bitSize(zcu);
+            // if (bit_size > 64) return .memory;
+            return .byval;
+        },
+        .@"enum", .error_set => {
+            const bit_size = ty.bitSize(zcu);
+            if (bit_size > 64) return .memory;
+            return .byval;
+        },
+        .vector => {
+            const bit_size = ty.bitSize(zcu);
+            // TODO is this controlled by a cpu feature?
+            if (ctx == .ret and bit_size > 128) return .memory;
+            if (bit_size > 512) return .memory;
+            return .byval;
+        },
+        .optional => {
+            assert(ty.isPtrLikeOptional(zcu));
+            return .byval;
+        },
+        .pointer => {
+            assert(!ty.isSlice(zcu));
+            return .byval;
+        },
+        .error_union,
+        .frame,
+        .@"anyframe",
+        .noreturn,
+        .void,
+        .type,
+        .comptime_float,
+        .comptime_int,
+        .undefined,
+        .null,
+        .@"fn",
+        .@"opaque",
+        .enum_literal,
+        .array,
+        => unreachable,
+    }
+}
+
+const byval_float_count = 4;
+fn countFloats(ty: Type, zcu: *Zcu, maybe_float_bits: *?u16) u32 {
+    const ip = &zcu.intern_pool;
+    const target = zcu.getTarget();
+    const invalid = std.math.maxInt(u32);
+    switch (ty.zigTypeTag(zcu)) {
+        .@"union" => {
+            const union_obj = zcu.typeToUnion(ty).?;
+            var max_count: u32 = 0;
+            for (union_obj.field_types.get(ip)) |field_ty| {
+                const field_count = countFloats(Type.fromInterned(field_ty), zcu, maybe_float_bits);
+                if (field_count == invalid) return invalid;
+                if (field_count > max_count) max_count = field_count;
+                if (max_count > byval_float_count) return invalid;
+            }
+            return max_count;
+        },
+        .@"struct" => {
+            const fields_len = ty.structFieldCount(zcu);
+            var count: u32 = 0;
+            var i: u32 = 0;
+            while (i < fields_len) : (i += 1) {
+                const field_ty = ty.fieldType(i, zcu);
+                const field_count = countFloats(field_ty, zcu, maybe_float_bits);
+                if (field_count == invalid) return invalid;
+                count += field_count;
+                if (count > byval_float_count) return invalid;
+            }
+            return count;
+        },
+        .float => {
+            const float_bits = maybe_float_bits.* orelse {
+                const float_bits = ty.floatBits(target);
+                if (float_bits != 32 and float_bits != 64) return invalid;
+                maybe_float_bits.* = float_bits;
+                return 1;
+            };
+            if (ty.floatBits(target) == float_bits) return 1;
+            return invalid;
+        },
+        .void => return 0,
+        else => return invalid,
+    }
+}