Codegen: use malloc_atomic whenever possible. Fixes #4081

Ary Borenszweig · Ary Borenszweig · commit f1998de803bc · 2017-03-03T10:37:10.000-03:00
diff --git a/src/compiler/crystal/codegen/codegen.cr b/src/compiler/crystal/codegen/codegen.cr
@@ -9,6 +9,7 @@ module Crystal
   MAIN_NAME          = "__crystal_main"
   RAISE_NAME         = "__crystal_raise"
   MALLOC_NAME        = "__crystal_malloc"
+  MALLOC_ATOMIC_NAME = "__crystal_malloc_atomic"
   REALLOC_NAME       = "__crystal_realloc"
   PERSONALITY_NAME   = "__crystal_personality"
   GET_EXCEPTION_NAME = "__crystal_get_exception"
@@ -129,6 +130,7 @@ module Crystal
     @empty_md_list : LLVM::Value
     @rescue_block : LLVM::BasicBlock?
     @malloc_fun : LLVM::Function?
+    @malloc_atomic_fun : LLVM::Function?
     @sret_value : LLVM::Value?
     @cant_pass_closure_to_c_exception_call : Call?
     @realloc_fun : LLVM::Function?
@@ -1746,7 +1748,12 @@ module Crystal
       if type.passed_by_value?
         @last = alloca struct_type
       else
-        @last = malloc struct_type
+        if type.is_a?(InstanceVarContainer) && !type.struct? &&
+           type.all_instance_vars.each_value.any? &.type.has_inner_pointers?
+          @last = malloc struct_type
+        else
+          @last = malloc_atomic struct_type
+        end
       end
       memset @last, int8(0), struct_type.size
       type_ptr = @last
@@ -1806,9 +1813,15 @@ module Crystal
     end
 
     def malloc(type)
-      @malloc_fun ||= @main_mod.functions[MALLOC_NAME]?
-      if malloc_fun = @malloc_fun
-        malloc_fun = check_main_fun MALLOC_NAME, malloc_fun
+      generic_malloc(type) { malloc_fun }
+    end
+
+    def malloc_atomic(type)
+      generic_malloc(type) { malloc_atomic_fun }
+    end
+
+    def generic_malloc(type)
+      if malloc_fun = yield
         size = trunc(type.size, llvm_context.int32)
         pointer = call malloc_fun, size
         bit_cast pointer, type.pointer
@@ -1818,12 +1831,18 @@ module Crystal
     end
 
     def array_malloc(type, count)
-      @malloc_fun ||= @main_mod.functions[MALLOC_NAME]?
+      generic_array_malloc(type, count) { malloc_fun }
+    end
+
+    def array_malloc_atomic(type, count)
+      generic_array_malloc(type, count) { malloc_atomic_fun }
+    end
+
+    def generic_array_malloc(type, count)
       size = trunc(type.size, llvm_context.int32)
       count = trunc(count, llvm_context.int32)
       size = builder.mul size, count
-      if malloc_fun = @malloc_fun
-        malloc_fun = check_main_fun MALLOC_NAME, malloc_fun
+      if malloc_fun = yield
         pointer = call malloc_fun, size
         memset pointer, int8(0), size
         bit_cast pointer, type.pointer
@@ -1835,6 +1854,24 @@ module Crystal
       end
     end
 
+    def malloc_fun
+      @malloc_fun ||= @main_mod.functions[MALLOC_NAME]?
+      if malloc_fun = @malloc_fun
+        check_main_fun MALLOC_NAME, malloc_fun
+      else
+        nil
+      end
+    end
+
+    def malloc_atomic_fun
+      @malloc_atomic_fun ||= @main_mod.functions[MALLOC_ATOMIC_NAME]?
+      if malloc_fun = @malloc_atomic_fun
+        check_main_fun MALLOC_ATOMIC_NAME, malloc_fun
+      else
+        nil
+      end
+    end
+
     def memset(pointer, value, size)
       pointer = cast_to_void_pointer pointer
       call @program.memset(@llvm_mod, llvm_context), [pointer, value, trunc(size, llvm_context.int32), int32(4), int1(0)]
diff --git a/src/compiler/crystal/codegen/primitives.cr b/src/compiler/crystal/codegen/primitives.cr
@@ -423,7 +423,11 @@ class Crystal::CodeGenVisitor
   def codegen_primitive_pointer_malloc(node, target_def, call_args)
     type = node.type.as(PointerInstanceType)
     llvm_type = llvm_embedded_type(type.element_type)
-    last = array_malloc(llvm_type, call_args[1])
+    if type.element_type.has_inner_pointers?
+      last = array_malloc(llvm_type, call_args[1])
+    else
+      last = array_malloc_atomic(llvm_type, call_args[1])
+    end
     last
   end
 
diff --git a/src/compiler/crystal/codegen/types.cr b/src/compiler/crystal/codegen/types.cr
@@ -39,6 +39,49 @@ module Crystal
       end
     end
 
+    # Returns `true` if the type has inner pointers.
+    # This is useful to know because if a type doesn't have
+    # inner pointers we can use `malloc_atomic` instead of
+    # `malloc` in `Pointer.malloc` for a tiny performance boost.
+    def has_inner_pointers?
+      case self
+      when void?
+        # We consider Void to have pointers, so doing
+        # Pointer(Void).malloc(...).as(ReferenceType)
+        # will consider potential inner pointers as such.
+        true
+      when PointerInstanceType
+        true
+      when ProcInstanceType
+        # A proc can have closure data which might have pointers
+        true
+      when StaticArrayInstanceType
+        self.element_type.has_inner_pointers?
+      when TupleInstanceType
+        self.tuple_types.any? &.has_inner_pointers?
+      when NamedTupleInstanceType
+        self.entries.any? &.type.has_inner_pointers?
+      when PrimitiveType
+        false
+      when EnumType
+        false
+      when UnionType
+        self.union_types.any? &.has_inner_pointers?
+      when AliasType
+        self.aliased_type.has_inner_pointers?
+      when TypeDefType
+        self.typedef.has_inner_pointers?
+      when InstanceVarContainer
+        if struct?
+          all_instance_vars.each_value.any? &.type.has_inner_pointers?
+        else
+          true
+        end
+      else
+        true
+      end
+    end
+
     def llvm_name
       String.build do |io|
         llvm_name io
