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>
---
 tcg/tcg.c | 78 +++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 56 insertions(+), 22 deletions(-)

diff --git a/tcg/tcg.c b/tcg/tcg.c
index aa13158999..216a6963b3 100644
--- 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;
+                }
             }
         }
     }
-- 
2.20.1