Implement Liquid::C::Expression to optimize expression evaluation

Rakefile

@@ -4,7 +4,7 @@ require 'bundler/gem_tasks'
 require 'rake/extensiontask'
 require 'benchmark'
 
-ENV['DEBUG'] = 'true'
+ENV['DEBUG'] ||= 'true'
 ext_task = Rake::ExtensionTask.new("liquid_c")
 
 # For MacOS, generate debug information that ruby can read

ext/liquid_c/c_buffer.h

@@ -54,4 +54,9 @@ inline void c_buffer_rb_gc_mark(c_buffer_t *buffer)
     }
 }
 
+inline void c_buffer_concat(c_buffer_t *dest, c_buffer_t *src)
+{
+    c_buffer_write(dest, src->data, c_buffer_size(src));
+}
+
 #endif

ext/liquid_c/context.c

@@ -2,32 +2,32 @@
 #include "context.h"
 #include "variable_lookup.h"
 #include "vm.h"
+#include "expression.h"
 
 static VALUE cLiquidVariableLookup, cLiquidUndefinedVariable;
 ID id_aset, id_set_context;
 static ID id_has_key, id_aref;
 static ID id_ivar_scopes, id_ivar_environments, id_ivar_static_environments, id_ivar_strict_variables;
 
-VALUE context_evaluate(VALUE self, VALUE expression)
+static VALUE context_evaluate(VALUE self, VALUE expression)
 {
-    // Scalar type stored directly in the VALUE, this is a nearly free check, saving a #respond_to?
+    // Scalar type stored directly in the VALUE, this needs to be checked anyways to use RB_BUILTIN_TYPE
     if (RB_SPECIAL_CONST_P(expression))
         return expression;
 
-    VALUE klass = RBASIC(expression)->klass;
-
-    // Basic types that do not respond to #evaluate
-    if (klass == rb_cString || klass == rb_cArray || klass == rb_cHash)
-        return expression;
-
-    // Liquid::VariableLookup is by far the most common type after String, call
-    // the C implementation directly to avoid a Ruby dispatch.
-    if (klass == cLiquidVariableLookup)
-        return variable_lookup_evaluate(expression, self);
-
-    if (rb_respond_to(expression, id_evaluate))
-        return rb_funcall(expression, id_evaluate, 1, self);
-
+    switch (RB_BUILTIN_TYPE(expression)) {
+        case T_DATA:
+            if (RBASIC_CLASS(expression) == cLiquidCExpression)
+                return internal_expression_evaluate(DATA_PTR(expression), self);
+            break; // e.g. BigDecimal
+        case T_OBJECT: // may be Liquid::VariableLookup or Liquid::RangeLookup
+        {
+            VALUE result = rb_check_funcall(expression, id_evaluate, 1, &self);
+            return RB_LIKELY(result != Qundef) ? result : expression;
+        }
+        default:
+            break;
+    }
     return expression;
 }
 

ext/liquid_c/context.h

@@ -2,7 +2,6 @@
 #define LIQUID_CONTEXT_H
 
 void init_liquid_context();
-VALUE context_evaluate(VALUE self, VALUE expression);
 VALUE context_find_variable(VALUE self, VALUE key, VALUE raise_on_not_found);
 void context_maybe_raise_undefined_variable(VALUE self, VALUE key);
 

ext/liquid_c/expression.c

@@ -0,0 +1,97 @@
+#include "liquid.h"
+#include "vm_assembler.h"
+#include "parser.h"
+#include "vm.h"
+#include "expression.h"
+
+VALUE cLiquidCExpression;
+
+static void expression_mark(void *ptr)
+{
+    expression_t *expression = ptr;
+    vm_assembler_gc_mark(&expression->code);
+}
+
+static void expression_free(void *ptr)
+{
+    expression_t *expression = ptr;
+    vm_assembler_free(&expression->code);
+    xfree(expression);
+}
+
+static size_t expression_memsize(const void *ptr)
+{
+    const expression_t *expression = ptr;
+    return sizeof(expression_t) + vm_assembler_alloc_memsize(&expression->code);
+}
+
+const rb_data_type_t expression_data_type = {
+    "liquid_expression",
+    { expression_mark, expression_free, expression_memsize, },
+    NULL, NULL, RUBY_TYPED_FREE_IMMEDIATELY
+};
+
+VALUE expression_new(expression_t **expression_ptr)
+{
+    expression_t *expression;
+    VALUE obj = TypedData_Make_Struct(cLiquidCExpression, expression_t, &expression_data_type, expression);
+    *expression_ptr = expression;
+    vm_assembler_init(&expression->code);
+    return obj;
+}
+
+static VALUE internal_expression_parse(parser_t *p)
+{
+    if (p->cur.type == TOKEN_EOS)
+        return Qnil;
+
+    // Avoid allocating an expression object just to wrap a constant
+    VALUE const_obj = try_parse_constant_expression(p);
+    if (const_obj != Qundef)
+        return const_obj;
+
+    expression_t *expression;
+    VALUE expr_obj = expression_new(&expression);
+
+    parse_and_compile_expression(p, &expression->code);
+    vm_assembler_add_leave(&expression->code);
+
+    return expr_obj;
+}
+
+static VALUE expression_strict_parse(VALUE klass, VALUE markup)
+{
+    StringValue(markup);
+    char *start = RSTRING_PTR(markup);
+
+    parser_t p;
+    init_parser(&p, start, start + RSTRING_LEN(markup));
+    VALUE expr_obj = internal_expression_parse(&p);
+
+    if (p.cur.type != TOKEN_EOS)
+        rb_enc_raise(utf8_encoding, cLiquidSyntaxError, "[:%s] is not a valid expression", symbol_names[p.cur.type]);
+
+    return expr_obj;
+}
+
+#define Expression_Get_Struct(obj, sval) TypedData_Get_Struct(obj, expression_t, &expression_data_type, sval)
+
+static VALUE expression_evaluate(VALUE self, VALUE context)
+{
+    expression_t *expression;
+    Expression_Get_Struct(self, expression);
+    return liquid_vm_evaluate(context, &expression->code);
+}
+
+VALUE internal_expression_evaluate(expression_t *expression, VALUE context)
+{
+    return liquid_vm_evaluate(context, &expression->code);
+}
+
+void init_liquid_expression()
+{
+    cLiquidCExpression = rb_define_class_under(mLiquidC, "Expression", rb_cObject);
+    rb_undef_alloc_func(cLiquidCExpression);
+    rb_define_singleton_method(cLiquidCExpression, "strict_parse", expression_strict_parse, 1);
+    rb_define_method(cLiquidCExpression, "evaluate", expression_evaluate, 1);
+}

ext/liquid_c/expression.h

@@ -0,0 +1,19 @@
+#if !defined(LIQUID_EXPRESSION_H)
+#define LIQUID_EXPRESSION_H
+
+#include "vm_assembler.h"
+#include "parser.h"
+
+extern VALUE cLiquidCExpression;
+
+typedef struct expression {
+    vm_assembler_t code;
+} expression_t;
+
+void init_liquid_expression();
+
+VALUE expression_new(expression_t **expression_ptr);
+VALUE internal_expression_evaluate(expression_t *expression, VALUE context);
+
+#endif
+

ext/liquid_c/extconf.rb

@@ -4,8 +4,12 @@
   $CFLAGS << ' -Werror'
 end
 compiler = RbConfig::MAKEFILE_CONFIG['CC']
-if ENV['DEBUG'] == 'true' && compiler =~ /gcc|g\+\+/
-  $CFLAGS << ' -fbounds-check'
+if ENV['DEBUG'] == 'true'
+  if compiler =~ /gcc|g\+\+/
+    $CFLAGS << ' -fbounds-check'
+  end
+else
+  $CFLAGS << ' -DNDEBUG'
 end
 
 if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("2.7.0") # added in 2.7

ext/liquid_c/lexer.h

@@ -42,8 +42,19 @@ inline static VALUE token_to_rstr(lexer_token_t token) {
     return rb_enc_str_new(token.val, token.val_end - token.val, utf8_encoding);
 }
 
+inline static VALUE token_check_for_symbol(lexer_token_t token) {
+    return rb_check_symbol_cstr(token.val, token.val_end - token.val, utf8_encoding);
+}
+
+inline static VALUE token_to_rstr_leveraging_existing_symbol(lexer_token_t token) {
+    VALUE sym = token_check_for_symbol(token);
+    if (RB_LIKELY(sym != Qnil))
+        return rb_sym2str(sym);
+    return token_to_rstr(token);
+}
+
 inline static VALUE token_to_rsym(lexer_token_t token) {
-    VALUE sym = rb_check_symbol_cstr(token.val, token.val_end - token.val, utf8_encoding);
+    VALUE sym = token_check_for_symbol(token);
     if (RB_LIKELY(sym != Qnil))
         return sym;
     return rb_str_intern(token_to_rstr(token));

ext/liquid_c/liquid.c

@@ -5,13 +5,15 @@
 #include "parser.h"
 #include "raw.h"
 #include "resource_limits.h"
+#include "expression.h"
 #include "block.h"
 #include "context.h"
 #include "variable_lookup.h"
 #include "vm.h"
 
 ID id_evaluate;
 ID id_to_liquid;
+ID id_to_s;
 ID id_call;
 
 VALUE mLiquid, mLiquidC, cLiquidVariable, cLiquidTemplate, cLiquidBlockBody;
@@ -28,6 +30,7 @@ void Init_liquid_c(void)
 {
     id_evaluate = rb_intern("evaluate");
     id_to_liquid = rb_intern("to_liquid");
+    id_to_s = rb_intern("to_s");
     id_call = rb_intern("call");
 
     utf8_encoding = rb_utf8_encoding();
@@ -61,6 +64,7 @@ void Init_liquid_c(void)
     init_liquid_parser();
     init_liquid_raw();
     init_liquid_resource_limits();
+    init_liquid_expression();
     init_liquid_variable();
     init_liquid_block();
     init_liquid_context();

ext/liquid_c/liquid.h

@@ -7,6 +7,7 @@
 
 extern ID id_evaluate;
 extern ID id_to_liquid;
+extern ID id_to_s;
 extern ID id_call;
 
 extern VALUE mLiquid, mLiquidC, cLiquidVariable, cLiquidTemplate, cLiquidBlockBody;