From dda21a25ca12c1d974ace0cb3ce52aa75003da6f Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Sun, 28 Jun 2026 17:10:32 -0700
Subject: [PATCH] spirv: make `@extern` support flat for outputs too

---
 src/Sema.zig                                                 | 5 +++--
 .../compile_errors/extern_spirv_decoration_validation.zig    | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/Sema.zig b/src/Sema.zig
index 2469444831e1037c7e526a33a0f4c2f39b26474a..10272d2a207a3b0b462df67c2a415141bf48d428 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -24966,8 +24966,9 @@ fn zirBuiltinExtern(
     }
 
     if (options.decoration) |decoration| switch (decoration) {
-        .flat => if (ptr_info.flags.address_space != .input) {
-            return sema.fail(block, options_src, "'flat' decoration requires 'input' address space", .{});
+        .flat => switch (ptr_info.flags.address_space) {
+            .input, .output => {},
+            else => return sema.fail(block, options_src, "\"flat\" decoration requires \"input\" or \"output\" address space", .{}),
         },
         .location, .descriptor => {},
     };
diff --git a/test/cases/compile_errors/extern_spirv_decoration_validation.zig b/test/cases/compile_errors/extern_spirv_decoration_validation.zig
index ea51feb3b931f5d6a93d8640a9a8819251bb3cfc..ae64963849857b2ba6b95f45b33c179b6700870b 100644
--- a/test/cases/compile_errors/extern_spirv_decoration_validation.zig
+++ b/test/cases/compile_errors/extern_spirv_decoration_validation.zig
@@ -1,4 +1,4 @@
-const x = @extern(*addrspace(.output) u32, .{
+const x = @extern(*addrspace(.push_constant) u32, .{
     .name = "x",
     .decoration = .{ .flat = 0 },
 });
@@ -10,4 +10,4 @@ comptime {
 // backend=selfhosted
 // target=spirv32-vulkan
 //
-// :1:45: error: 'flat' decoration requires 'input' address space
+// :1:45: error: "flat" decoration requires "input" or "output" address space
-- 
2.54.0