tint/resolver: Materialize argument to bitcast

Bug: tint:1504
Change-Id: I4eb4f041e69154dccd9719746a30dd6963dcd252
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/91846
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: David Neto <dneto@google.com>

src/tint/resolver/materialize_test.cc

@@ -544,6 +544,12 @@ enum class Method {
     // min(abstract_expr, abstract_expr);
     kBuiltinArg,
 
+    // bitcast<f32>(abstract_expr);
+    kBitcastF32Arg,
+
+    // bitcast<vec3<f32>>(abstract_expr);
+    kBitcastVec3F32Arg,
+
     // array<i32, abstract_expr>();
     kArrayLength,
 
@@ -562,6 +568,10 @@ static std::ostream& operator<<(std::ostream& o, Method m) {
             return o << "let";
         case Method::kBuiltinArg:
             return o << "builtin-arg";
+        case Method::kBitcastF32Arg:
+            return o << "bitcast-f32-arg";
+        case Method::kBitcastVec3F32Arg:
+            return o << "bitcast-vec3-f32-arg";
         case Method::kArrayLength:
             return o << "array-length";
         case Method::kSwitch:
@@ -632,6 +642,12 @@ TEST_P(MaterializeAbstractNumericToDefaultType, Test) {
         case Method::kBuiltinArg:
             WrapInFunction(CallStmt(Call("min", abstract_expr(), abstract_expr())));
             break;
+        case Method::kBitcastF32Arg:
+            WrapInFunction(Bitcast<f32>(abstract_expr()));
+            break;
+        case Method::kBitcastVec3F32Arg:
+            WrapInFunction(Bitcast(ty.vec3<f32>(), abstract_expr()));
+            break;
         case Method::kArrayLength:
             WrapInFunction(Construct(ty.array(ty.i32(), abstract_expr())));
             break;
@@ -701,6 +717,7 @@ constexpr Method kScalarMethods[] = {
     Method::kLet,
     Method::kVar,
     Method::kBuiltinArg,
+    Method::kBitcastF32Arg,
 };
 
 /// Methods that support vector materialization
@@ -708,6 +725,7 @@ constexpr Method kVectorMethods[] = {
     Method::kLet,
     Method::kVar,
     Method::kBuiltinArg,
+    Method::kBitcastVec3F32Arg,
 };
 
 /// Methods that support matrix materialization

src/tint/resolver/resolver.cc

@@ -1239,7 +1239,10 @@ sem::Expression* Resolver::IndexAccessor(const ast::IndexAccessorExpression* exp
 }
 
 sem::Expression* Resolver::Bitcast(const ast::BitcastExpression* expr) {
-    auto* inner = sem_.Get(expr->expr);
+    auto* inner = Materialize(sem_.Get(expr->expr));
+    if (!inner) {
+        return nullptr;
+    }
     auto* ty = Type(expr->type);
     if (!ty) {
         return nullptr;