[WGSL] Field access should support pointers

https://bugs.webkit.org/show_bug.cgi?id=272838
rdar://126621076

Reviewed by Mike Wyrzykowski.

The WGSL spec was updated to support struct field access on pointers (e.g. (&x).y),
and while the type checker was updated to support it, there were a couple other
changes necessary:
- the renamer/mangler did not correctly rename the field when accessing a pointer
- the global rewriter asserted that the base should be either a reference or a struct
- the code generator was not emitting the correct code (i.e. x->y instead of x.y)

* Source/WebGPU/WGSL/GlobalVariableRewriter.cpp:
(WGSL::RewriteGlobalVariables::getPacking):
* Source/WebGPU/WGSL/MangleNames.cpp:
(WGSL::NameManglerVisitor::visit):
* Source/WebGPU/WGSL/Metal/MetalFunctionWriter.cpp:
(WGSL::Metal::FunctionDefinitionWriter::visit):
* Source/WebGPU/WGSL/tests/valid/access-expression.wgsl:

Canonical link: https://commits.webkit.org/277665@main

Author: tadeuzagallo

Source/WebGPU/WGSL/GlobalVariableRewriter.cpp

@@ -474,6 +474,8 @@ Packing RewriteGlobalVariables::getPacking(AST::CallExpression& call)
                     auto* type = base.inferredType();
                     if (auto* reference = std::get_if<Types::Reference>(type))
                         type = reference->element;
+                    if (auto* pointer = std::get_if<Types::Pointer>(type))
+                        type = pointer->element;
                     auto& structure = std::get<Types::Struct>(*type).structure;
                     auto& lastMember = structure.members().last();
                     RELEASE_ASSERT(lastMember.name().id() == fieldAccess->fieldName().id());

Source/WebGPU/WGSL/MangleNames.cpp

@@ -163,6 +163,8 @@ void NameManglerVisitor::visit(AST::FieldAccessExpression& access)
     auto* baseType = access.base().inferredType();
     if (auto* reference = std::get_if<Types::Reference>(baseType))
         baseType = reference->element;
+    if (auto* pointer = std::get_if<Types::Pointer>(baseType))
+        baseType = pointer->element;
     auto* structType = std::get_if<Types::Struct>(baseType);
     if (!structType)
         return;

Source/WebGPU/WGSL/Metal/MetalFunctionWriter.cpp

@@ -2080,7 +2080,12 @@ void FunctionDefinitionWriter::visit(AST::IdentifierExpression& identifier)
 void FunctionDefinitionWriter::visit(AST::FieldAccessExpression& access)
 {
     visit(access.base());
-    m_stringBuilder.append(".", access.fieldName());
+    auto* baseType = access.base().inferredType();
+    if (baseType && std::holds_alternative<Types::Pointer>(*baseType))
+        m_stringBuilder.append("->");
+    else
+        m_stringBuilder.append(".");
+    m_stringBuilder.append(access.fieldName());
 }
 
 void FunctionDefinitionWriter::visit(AST::BoolLiteral& literal)

Source/WebGPU/WGSL/tests/valid/access-expression.wgsl

@@ -227,4 +227,9 @@ fn testStructAccessExpression()
     var s: S;
     let x: i32 = s.x;
     s.x = 0;
+
+    {
+      let s = &s;
+      s.x = 0;
+    }
 }