ADD_HIDDEN_SMART = 2, /**< add hidden parameters last for non-variadic and first for variadic functions. */
} add_hidden;
+/**
+ * Additional flags for the lowering.
+ */
+enum lowering_flags {
+ LF_NONE = 0, /**< no additional flags */
+ LF_COMPOUND_PARAM = 1, /**< lower calls with compound parameters */
+ LF_COMPOUND_RETURN = 2, /**< lower calls with compound returns */
+ LF_RETURN_HIDDEN = 4, /**< return the hidden address instead of void */
+ LF_SMALL_CMP_IN_REGS = 8 /**< return small compound values in registers */
+};
+
+/** Maximum number of registers that can be used to return compound values. */
+#define MAX_REGISTER_RET_VAL 2
+
+/**
+ * A struct containing all control parameters for
+ * lower_compound_ret_calls().
+ */
typedef struct {
- int def_ptr_alignment; /**< default alignment for data pointer */
- add_hidden hidden_params; /**< where to add hidden params. */
+ int def_ptr_alignment; /**< Default alignment for data pointer. */
+ unsigned flags; /**< A bitmask of enum lowering_flags. */
+ add_hidden hidden_params; /**< Where to add hidden parameters. */
- /** a function returning a pointer type for a given type */
+ /**
+ * A function returning a pointer type for a given type.
+ * If this pointer is NULL, a new pointer type is always created.
+ */
ir_type *(*find_pointer_type)(ir_type *e_type, ir_mode *mode, int alignment);
+
+ /**
+ * If the LF_SMALL_CMP_IN_REGS flag is set, this function will be called
+ * to decide, whether a compound value should be returned in registers.
+ * This function must return the number of used registers and fill in the modes
+ * of the registers to use. Up to MAX_REGISTER_RET_VAL registers can be used.
+ */
+ int (*ret_compound_in_regs)(ir_type *compound_tp, ir_mode **modes);
} lower_params_t;
/**
- * Lower calls with compound return types.
+ * Lower calls with compound parameter and return types.
* This function does the following transformations:
*
+ * If LF_COMPOUND_PARAM is set:
+ *
+ * - Copy compound parameters to a new location on the callers
+ * stack and transmit the address of this new location
+ *
+ * If LF_COMPOUND_RETURN is set:
+ *
* - Adds a new (hidden) pointer parameter for
- * any return compound type.
+ * any return compound type. The return type is replaced by void
+ * or if LOWERING_FLAGS_RETURN_HIDDEN is set by the address.
*
* - Use of the hidden parameters in the function code.
*
* stack.
*
* - Replace a possible block copy after the function call.
+ *
+ * General:
+ *
+ * - Changes the types of methods and calls to the lowered ones
+ *
+ * - lower all method types of existing entities
+ *
+ * In pseudo-code, the following transformation is done:
+ *
+ @code
+ struct x ret = func(a, b);
+ @endcode
+ *
+ * is translated into
+ @code
+ struct x ret;
+ func(&ret, a, b);
+ @endcode
+ *
+ * If the function returns only one possible result, the copy-on-return
+ * optimization is done, ie.
+ @code
+ struct x func(a) {
+ struct x ret;
+ ret.a = a;
+ return ret;
+ }
+ @endcode
+ *
+ * is transformed into
+ *
+ @code
+ void func(struct x *ret, a) {
+ ret->a = a;
+ }
+ @endcode
+ *
+ * @param params A structure containing the control parameter for this
+ * transformation.
+ *
+ * During the transformation, pointer types must be created or reused.
+ * The caller can provide params->find_pointer_type for this task to
+ * reduce the number of created pointer types.
+ * If params->find_pointer_type is NULL, new pointer types
+ * are always created automatically.
*/
-void lower_compound_ret_calls(const lower_params_t *params);
+void lower_calls_with_compounds(const lower_params_t *params);
#endif /* _LOWER_CALLS_H_ */