/**
* @file
- * @brief Lower small CopyB nodes into a series of Load/store
- * @author Michael Beck, Matthias Braun
- * @version $Id$
+ * @brief Lower small CopyB nodes into a series of Load/Store nodes
+ * @author Michael Beck, Matthias Braun, Manuel Mohr
*/
#include "config.h"
#include "irtools.h"
#include "irgmod.h"
#include "error.h"
+#include "be.h"
typedef struct entry entry_t;
struct entry {
ir_node *copyb;
};
+/**
+ * Every CopyB is assigned a size category as follows:
+ * - 'small' iff size <= max_small_size,
+ * - 'medium' iff max_small_size < size < min_large_size,
+ * - 'large' iff size >= min_large_size.
+ *
+ * The idea is that each backend can apply different optimizations in each
+ * of the three categories.
+ *
+ * For small CopyBs, the x86 backend could, e.g., emit a single SSE
+ * instruction to copy 16 bytes. Other backends might just go with a series
+ * of Load/Stores. Therefore, x86 would like to keep the small CopyB nodes
+ * around whereas other backends would not.
+ * For medium-sized CopyBs, the x86 backend might generate a rep-prefixed mov
+ * instruction. Hence, it also wants to keep the CopyBs in these cases. Other
+ * backends might handle this differently.
+ * For large CopyBs, a call to memcpy is worth the call overhead, so large
+ * CopyBs should always be lowered to memcpy calls.
+ *
+ * The lowerer performs the following actions if the CopyB is
+ * - 'small': Replace it with a series of Loads/Stores
+ * - 'medium': Nothing.
+ * - 'large': Replace it with a call to memcpy.
+ *
+ * max_small_size and min_large_size allow for a flexible configuration.
+ * For example, one backend could specify max_small_size == 0 and
+ * min_large_size == 8192 to keep all CopyB nodes smaller than 8192 and get
+ * memcpy Calls for all others. Here, the set of small CopyBs is empty.
+ * Another backend could specify max_small_size == 63 and min_large_size == 64
+ * to lower all small CopyBs to Loads/Stores and all big CopyBs to memcpy.
+ * Hence, the set of medium-sized CopyBs is empty and this backend never
+ * sees a CopyB node at all.
+ * If memcpy is not available, min_large_size can be set to UINT_MAX to prevent
+ * the creation of calls to memcpy. Note that CopyBs whose size is UINT_MAX
+ * will still be lowered to memcpy calls because we check if the size is greater
+ * *or equal* to min_large_size. However, this should never occur in practice.
+ */
+
+static unsigned max_small_size; /**< The maximum size of a CopyB node
+ so that it is regarded as 'small'. */
+static unsigned min_large_size; /**< The minimum size of a CopyB node
+ so that it is regarded as 'large'. */
+static unsigned native_mode_bytes; /**< The size of the native mode in bytes. */
+static int allow_misalignments; /**< Whether backend can handle misaligned
+ loads and stores. */
+
typedef struct walk_env {
- unsigned max_size;
- struct obstack obst; /**< the obstack where data is allocated on */
- struct list_head list; /**< the list of copyb nodes */
+ struct obstack obst; /**< the obstack where data is allocated
+ on. */
+ struct list_head list; /**< the list of copyb nodes. */
} walk_env_t;
-static ir_mode *get_ir_mode(unsigned bytes)
+static ir_mode *get_ir_mode(unsigned mode_bytes)
{
- switch (bytes) {
+ switch (mode_bytes) {
case 1: return mode_Bu;
case 2: return mode_Hu;
case 4: return mode_Iu;
}
/**
- * lower a CopyB node.
+ * Turn a small CopyB node into a series of Load/Store nodes.
*/
-static void lower_copyb_nodes(ir_node *irn, unsigned mode_bytes)
+static void lower_small_copyb_node(ir_node *irn)
{
- ir_graph *irg = get_irn_irg(irn);
- unsigned size;
- unsigned offset;
- ir_mode *mode;
- ir_mode *addr_mode;
- ir_node *mem;
- ir_node *addr_src;
- ir_node *addr_dst;
- ir_node *block;
- ir_type *tp;
-
- addr_src = get_CopyB_src(irn);
- addr_dst = get_CopyB_dst(irn);
- mem = get_CopyB_mem(irn);
- addr_mode = get_irn_mode(addr_src);
- block = get_nodes_block(irn);
-
- tp = get_CopyB_type(irn);
- size = get_type_size_bytes(tp);
-
- offset = 0;
+ ir_graph *irg = get_irn_irg(irn);
+ ir_node *block = get_nodes_block(irn);
+ ir_type *tp = get_CopyB_type(irn);
+ ir_node *addr_src = get_CopyB_src(irn);
+ ir_node *addr_dst = get_CopyB_dst(irn);
+ ir_node *mem = get_CopyB_mem(irn);
+ ir_mode *addr_mode = get_irn_mode(addr_src);
+ unsigned mode_bytes = allow_misalignments ? native_mode_bytes : tp->align;
+ unsigned size = get_type_size_bytes(tp);
+ unsigned offset = 0;
+ ir_mode *mode;
+
while (offset < size) {
mode = get_ir_mode(mode_bytes);
for (; offset + mode_bytes <= size; offset += mode_bytes) {
mode_bytes /= 2;
}
- turn_into_tuple(irn, pn_CopyB_max);
+ turn_into_tuple(irn, pn_CopyB_max+1);
set_Tuple_pred(irn, pn_CopyB_M, mem);
- set_Tuple_pred(irn, pn_CopyB_X_regular, get_irg_bad(irg));
- set_Tuple_pred(irn, pn_CopyB_X_except, get_irg_bad(irg));
+ set_Tuple_pred(irn, pn_CopyB_X_regular, new_r_Bad(irg, mode_X));
+ set_Tuple_pred(irn, pn_CopyB_X_except, new_r_Bad(irg, mode_X));
+}
+
+static ir_type *get_memcpy_methodtype(void)
+{
+ ir_type *tp = new_type_method(3, 1);
+ ir_mode *size_t_mode = get_ir_mode(native_mode_bytes);
+
+ set_method_param_type(tp, 0, get_type_for_mode(mode_P));
+ set_method_param_type(tp, 1, get_type_for_mode(mode_P));
+ set_method_param_type(tp, 2, get_type_for_mode(size_t_mode));
+ set_method_res_type (tp, 0, get_type_for_mode(mode_P));
+
+ return tp;
+}
+
+static ir_node *get_memcpy_symconst(ir_graph *irg)
+{
+ ident *id = new_id_from_str("memcpy");
+ ir_type *mt = get_memcpy_methodtype();
+ ir_entity *ent = create_compilerlib_entity(id, mt);
+ symconst_symbol sym;
+
+ sym.entity_p = ent;
+ return new_r_SymConst(irg, mode_P_code, sym, symconst_addr_ent);
}
/**
- * Post-Walker: find small CopyB nodes.
+ * Turn a large CopyB node into a memcpy call.
+ */
+static void lower_large_copyb_node(ir_node *irn)
+{
+ ir_graph *irg = get_irn_irg(irn);
+ ir_node *block = get_nodes_block(irn);
+ dbg_info *dbgi = get_irn_dbg_info(irn);
+ ir_node *mem = get_CopyB_mem(irn);
+ ir_node *addr_src = get_CopyB_src(irn);
+ ir_node *addr_dst = get_CopyB_dst(irn);
+ ir_type *copyb_tp = get_CopyB_type(irn);
+ unsigned size = get_type_size_bytes(copyb_tp);
+
+ ir_node *symconst = get_memcpy_symconst(irg);
+ ir_type *call_tp = get_memcpy_methodtype();
+ ir_mode *mode_size_t = get_ir_mode(native_mode_bytes);
+ ir_node *in[3];
+ ir_node *call;
+ ir_node *call_mem;
+
+ in[0] = addr_dst;
+ in[1] = addr_src;
+ in[2] = new_r_Const_long(irg, mode_size_t, size);
+ call = new_rd_Call(dbgi, block, mem, symconst, 3, in, call_tp);
+ call_mem = new_r_Proj(call, mode_M, pn_Call_M);
+
+ turn_into_tuple(irn, 1);
+ set_irn_n(irn, pn_CopyB_M, call_mem);
+}
+
+static void lower_copyb_node(ir_node *irn)
+{
+ ir_type *tp = get_CopyB_type(irn);
+ unsigned size = get_type_size_bytes(tp);
+
+ if (size <= max_small_size)
+ lower_small_copyb_node(irn);
+ else if (size >= min_large_size)
+ lower_large_copyb_node(irn);
+ else
+ assert(!"CopyB of invalid size handed to lower_copyb_node");
+}
+
+/**
+ * Post-Walker: find CopyB nodes.
*/
static void find_copyb_nodes(ir_node *irn, void *ctx)
{
ir_type *tp;
unsigned size;
entry_t *entry;
+ bool medium_sized;
if (is_Proj(irn)) {
ir_node *pred = get_Proj_pred(irn);
if (get_type_state(tp) != layout_fixed)
return;
- size = get_type_size_bytes(tp);
- if (size > env->max_size)
- return;
+ size = get_type_size_bytes(tp);
+ medium_sized = max_small_size < size && size < min_large_size;
+ if (medium_sized)
+ return; /* Nothing to do for medium-sized CopyBs. */
- /* ok, link it in */
+ /* Okay, either small or large CopyB, so link it in and lower it later. */
entry = OALLOC(&env->obst, entry_t);
entry->copyb = irn;
INIT_LIST_HEAD(&entry->list);
list_add_tail(&entry->list, &env->list);
}
-void lower_CopyB(ir_graph *irg, unsigned max_size, unsigned native_mode_bytes)
+void lower_CopyB(ir_graph *irg, unsigned max_small_sz, unsigned min_large_sz,
+ int allow_misaligns)
{
- walk_env_t env;
- entry_t *entry;
- bool changed = false;
+ const backend_params *bparams = be_get_backend_param();
+ walk_env_t env;
+
+ assert(max_small_sz < min_large_sz && "CopyB size ranges must not overlap");
+
+ max_small_size = max_small_sz;
+ min_large_size = min_large_sz;
+ native_mode_bytes = bparams->machine_size / 8;
+ allow_misalignments = allow_misaligns;
obstack_init(&env.obst);
- env.max_size = max_size;
INIT_LIST_HEAD(&env.list);
irg_walk_graph(irg, NULL, find_copyb_nodes, &env);
list_for_each_entry(entry_t, entry, &env.list, list) {
- lower_copyb_nodes(entry->copyb, native_mode_bytes);
- changed = true;
- }
-
- if (changed) {
- set_irg_outs_inconsistent(irg);
- set_irg_loopinfo_inconsistent(irg);
+ lower_copyb_node(entry->copyb);
}
obstack_free(&env.obst, NULL);
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