Sema: only ABI sized packed structs are extern compatible

2 files changed, 20 insertions, 0 deletions

diff --git a/src/arch/wasm/abi.zig b/src/arch/wasm/abi.zig
index b1e99f4f92..d54965a50c 100644
--- a/src/arch/wasm/abi.zig
+++ b/src/arch/wasm/abi.zig
@@ -23,6 +23,10 @@ pub fn classifyType(ty: Type, target: Target) [2]Class {
     if (!ty.hasRuntimeBitsIgnoreComptime()) return none;
     switch (ty.zigTypeTag()) {
         .Struct => {
+            if (ty.containerLayout() == .Packed) {
+                if (ty.bitSize(target) <= 64) return direct;
+                return .{ .direct, .direct };
+            }
             // When the struct type is non-scalar
             if (ty.structFieldCount() > 1) return memory;
             // When the struct's alignment is non-natural
@@ -57,6 +61,10 @@ pub fn classifyType(ty: Type, target: Target) [2]Class {
             return direct;
         },
         .Union => {
+            if (ty.containerLayout() == .Packed) {
+                if (ty.bitSize(target) <= 64) return direct;
+                return .{ .direct, .direct };
+            }
             const layout = ty.unionGetLayout(target);
             std.debug.assert(layout.tag_size == 0);
             if (ty.unionFields().count() > 1) return memory;
diff --git a/src/arch/x86_64/abi.zig b/src/arch/x86_64/abi.zig
index 7e2025a23d..7fede95155 100644
--- a/src/arch/x86_64/abi.zig
+++ b/src/arch/x86_64/abi.zig
@@ -174,6 +174,12 @@ pub fn classifySystemV(ty: Type, target: Target) [8]Class {
             // "If the size of the aggregate exceeds a single eightbyte, each is classified
             // separately.".
             const ty_size = ty.abiSize(target);
+            if (ty.containerLayout() == .Packed) {
+                assert(ty_size <= 128);
+                result[0] = .integer;
+                if (ty_size > 64) result[1] = .integer;
+                return result;
+            }
             if (ty_size > 64)
                 return memory_class;
 
@@ -284,6 +290,12 @@ pub fn classifySystemV(ty: Type, target: Target) [8]Class {
             // "If the size of the aggregate exceeds a single eightbyte, each is classified
             // separately.".
             const ty_size = ty.abiSize(target);
+            if (ty.containerLayout() == .Packed) {
+                assert(ty_size <= 128);
+                result[0] = .integer;
+                if (ty_size > 64) result[1] = .integer;
+                return result;
+            }
             if (ty_size > 64)
                 return memory_class;