tcg: Improve move ops in liveness_pass_2

If the output of the move is dead, then the last use is in
the store.  If we propagate the input to the store, then we
can remove the move opcode entirely.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

diff --git a/tcg/tcg.c b/tcg/tcg.c
index 97558ec068f4a5a832b97cf95515d8cb23928336..1aa6cb47f291f770ee5fe9ac1d3ddd8e50a28303 100644 (file)
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -2982,34 +2982,68 @@ static bool liveness_pass_2(TCGContext *s)
         }
 
         /* Outputs become available.  */
-        for (i = 0; i < nb_oargs; i++) {
-            arg_ts = arg_temp(op->args[i]);
+        if (opc == INDEX_op_mov_i32 || opc == INDEX_op_mov_i64) {
+            arg_ts = arg_temp(op->args[0]);
             dir_ts = arg_ts->state_ptr;
-            if (!dir_ts) {
-                continue;
+            if (dir_ts) {
+                op->args[0] = temp_arg(dir_ts);
+                changes = true;
+
+                /* The output is now live and modified.  */
+                arg_ts->state = 0;
+
+                if (NEED_SYNC_ARG(0)) {
+                    TCGOpcode sopc = (arg_ts->type == TCG_TYPE_I32
+                                      ? INDEX_op_st_i32
+                                      : INDEX_op_st_i64);
+                    TCGOp *sop = tcg_op_insert_after(s, op, sopc);
+                    TCGTemp *out_ts = dir_ts;
+
+                    if (IS_DEAD_ARG(0)) {
+                        out_ts = arg_temp(op->args[1]);
+                        arg_ts->state = TS_DEAD;
+                        tcg_op_remove(s, op);
+                    } else {
+                        arg_ts->state = TS_MEM;
+                    }
+
+                    sop->args[0] = temp_arg(out_ts);
+                    sop->args[1] = temp_arg(arg_ts->mem_base);
+                    sop->args[2] = arg_ts->mem_offset;
+                } else {
+                    tcg_debug_assert(!IS_DEAD_ARG(0));
+                }
             }
-            op->args[i] = temp_arg(dir_ts);
-            changes = true;
+        } else {
+            for (i = 0; i < nb_oargs; i++) {
+                arg_ts = arg_temp(op->args[i]);
+                dir_ts = arg_ts->state_ptr;
+                if (!dir_ts) {
+                    continue;
+                }
+                op->args[i] = temp_arg(dir_ts);
+                changes = true;
 
-            /* The output is now live and modified.  */
-            arg_ts->state = 0;
+                /* The output is now live and modified.  */
+                arg_ts->state = 0;
 
-            /* Sync outputs upon their last write.  */
-            if (NEED_SYNC_ARG(i)) {
-                TCGOpcode sopc = (arg_ts->type == TCG_TYPE_I32
-                                  ? INDEX_op_st_i32
-                                  : INDEX_op_st_i64);
-                TCGOp *sop = tcg_op_insert_after(s, op, sopc);
+                /* Sync outputs upon their last write.  */
+                if (NEED_SYNC_ARG(i)) {
+                    TCGOpcode sopc = (arg_ts->type == TCG_TYPE_I32
+                                      ? INDEX_op_st_i32
+                                      : INDEX_op_st_i64);
+                    TCGOp *sop = tcg_op_insert_after(s, op, sopc);
 
-                sop->args[0] = temp_arg(dir_ts);
-                sop->args[1] = temp_arg(arg_ts->mem_base);
-                sop->args[2] = arg_ts->mem_offset;
+                    sop->args[0] = temp_arg(dir_ts);
+                    sop->args[1] = temp_arg(arg_ts->mem_base);
+                    sop->args[2] = arg_ts->mem_offset;
 
-                arg_ts->state = TS_MEM;
-            }
-            /* Drop outputs that are dead.  */
-            if (IS_DEAD_ARG(i)) {
-                arg_ts->state = TS_DEAD;
+                    arg_ts->state = TS_MEM;
+                }
+                /* Drop outputs that are dead.  */
+                if (IS_DEAD_ARG(i)) {
+                    arg_ts->state = TS_DEAD;
+                }
             }
         }
     }