From 50a771a11ed1604d642e94219ac1e939c249f6da Mon Sep 17 00:00:00 2001
From: Robin Voetter <robin@voetter.nl>
Date: Sat, 15 Jun 2024 14:17:07 +0200
Subject: spirv: add support for workItemId, workGroupId, workGroupSize

---
 src/codegen/spirv/Module.zig | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

(limited to 'src/codegen/spirv/Module.zig')

diff --git a/src/codegen/spirv/Module.zig b/src/codegen/spirv/Module.zig
index d1b2171786..ae30de156b 100644
--- a/src/codegen/spirv/Module.zig
+++ b/src/codegen/spirv/Module.zig
@@ -8,7 +8,6 @@
 const Module = @This();
 
 const std = @import("std");
-const builtin = @import("builtin");
 const Allocator = std.mem.Allocator;
 const assert = std.debug.assert;
 
@@ -150,6 +149,8 @@ strings: std.StringArrayHashMapUnmanaged(IdRef) = .{},
 /// this is an ad-hoc structure to cache types where required.
 /// According to the SPIR-V specification, section 2.8, this includes all non-aggregate
 /// non-pointer types.
+/// Additionally, this is used for other values which can be cached, for example,
+/// built-in variables.
 cache: struct {
     bool_type: ?IdRef = null,
     void_type: ?IdRef = null,
@@ -158,6 +159,8 @@ cache: struct {
     // This cache is required so that @Vector(X, u1) in direct representation has the
     // same ID as @Vector(X, bool) in indirect representation.
     vector_types: std.AutoHashMapUnmanaged(struct { IdRef, u32 }, IdRef) = .{},
+
+    builtins: std.AutoHashMapUnmanaged(struct { IdRef, spec.BuiltIn }, Decl.Index) = .{},
 } = .{},
 
 /// Set of Decls, referred to by Decl.Index.
@@ -198,6 +201,7 @@ pub fn deinit(self: *Module) void {
     self.cache.int_types.deinit(self.gpa);
     self.cache.float_types.deinit(self.gpa);
     self.cache.vector_types.deinit(self.gpa);
+    self.cache.builtins.deinit(self.gpa);
 
     self.decls.deinit(self.gpa);
     self.decl_deps.deinit(self.gpa);
@@ -491,6 +495,25 @@ pub fn vectorType(self: *Module, len: u32, child_id: IdRef) !IdRef {
     return entry.value_ptr.*;
 }
 
+/// Return a pointer to a builtin variable. `result_ty_id` must be a **pointer**
+/// with storage class `.Input`.
+pub fn builtin(self: *Module, result_ty_id: IdRef, spirv_builtin: spec.BuiltIn) !Decl.Index {
+    const entry = try self.cache.builtins.getOrPut(self.gpa, .{ result_ty_id, spirv_builtin });
+    if (!entry.found_existing) {
+        const decl_index = try self.allocDecl(.global);
+        const result_id = self.declPtr(decl_index).result_id;
+        entry.value_ptr.* = decl_index;
+        try self.sections.types_globals_constants.emit(self.gpa, .OpVariable, .{
+            .id_result_type = result_ty_id,
+            .id_result = result_id,
+            .storage_class = .Input,
+        });
+        try self.decorate(result_id, .{ .BuiltIn = .{ .built_in = spirv_builtin } });
+        try self.declareDeclDeps(decl_index, &.{});
+    }
+    return entry.value_ptr.*;
+}
+
 pub fn constUndef(self: *Module, ty_id: IdRef) !IdRef {
     const result_id = self.allocId();
     try self.sections.types_globals_constants.emit(self.gpa, .OpUndef, .{
-- 
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