[Qemu-devel] [PATCH 3/6] Do constant folding for basic arithmetic operations.

[Kirill Batuzov]

Perform actual constant folding for ADD, SUB and MUL operations.

Signed-off-by: Kirill Batuzov <address@hidden>
---
 tcg/optimize.c |  102 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 102 insertions(+), 0 deletions(-)

diff --git a/tcg/optimize.c b/tcg/optimize.c
index a761c51..4073f05 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -82,6 +82,79 @@ static void reset_temp(tcg_temp_state *state, 
tcg_target_ulong *vals,
     state[temp] = TCG_TEMP_ANY;
 }
 
+static int op_bits(int op)
+{
+    switch (op) {
+    case INDEX_op_mov_i32:
+    case INDEX_op_add_i32:
+    case INDEX_op_sub_i32:
+    case INDEX_op_mul_i32:
+        return 32;
+#if TCG_TARGET_REG_BITS == 64
+    case INDEX_op_mov_i64:
+    case INDEX_op_add_i64:
+    case INDEX_op_sub_i64:
+    case INDEX_op_mul_i64:
+        return 64;
+#endif
+    default:
+        fprintf(stderr, "Unrecognized operation %d in op_bits.\n", op);
+        tcg_abort();
+    }
+}
+
+static int op_to_movi(int op)
+{
+    if (op_bits(op) == 32) {
+        return INDEX_op_movi_i32;
+    }
+#if TCG_TARGET_REG_BITS == 64
+    if (op_bits(op) == 64) {
+        return INDEX_op_movi_i64;
+    }
+#endif
+    tcg_abort();
+}
+
+static TCGArg do_constant_folding_2(int op, TCGArg x, TCGArg y)
+{
+    switch (op) {
+    case INDEX_op_add_i32:
+#if TCG_TARGET_REG_BITS == 64
+    case INDEX_op_add_i64:
+#endif
+        return x + y;
+
+    case INDEX_op_sub_i32:
+#if TCG_TARGET_REG_BITS == 64
+    case INDEX_op_sub_i64:
+#endif
+        return x - y;
+
+    case INDEX_op_mul_i32:
+#if TCG_TARGET_REG_BITS == 64
+    case INDEX_op_mul_i64:
+#endif
+        return x * y;
+
+    default:
+        fprintf(stderr,
+                "Unrecognized operation %d in do_constant_folding.\n", op);
+        tcg_abort();
+    }
+}
+
+static TCGArg do_constant_folding(int op, TCGArg x, TCGArg y)
+{
+    TCGArg res = do_constant_folding_2(op, x, y);
+#if TCG_TARGET_REG_BITS == 64
+    if (op_bits(op) == 32) {
+        res &= 0xffffffff;
+    }
+#endif
+    return res;
+}
+
 /* Propagate constants and copies, fold constant expressions. */
 static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
                                     TCGArg *args, TCGOpDef *tcg_op_defs)
@@ -164,6 +237,35 @@ static TCGArg *tcg_constant_folding(TCGContext *s, 
uint16_t *tcg_opc_ptr,
             gen_args += 2;
             args += 2;
             break;
+        case INDEX_op_add_i32:
+        case INDEX_op_sub_i32:
+        case INDEX_op_mul_i32:
+#if TCG_TARGET_REG_BITS == 64
+        case INDEX_op_add_i64:
+        case INDEX_op_sub_i64:
+        case INDEX_op_mul_i64:
+#endif
+            if (state[args[1]] == TCG_TEMP_CONST
+                && state[args[2]] == TCG_TEMP_CONST) {
+                gen_opc_buf[op_index] = op_to_movi(op);
+                gen_args[0] = args[0];
+                gen_args[1] =
+                    do_constant_folding(op, vals[args[1]], vals[args[2]]);
+                reset_temp(state, vals, gen_args[0], nb_temps, nb_globals);
+                state[gen_args[0]] = TCG_TEMP_CONST;
+                vals[gen_args[0]] = gen_args[1];
+                gen_args += 2;
+                args += 3;
+                break;
+            } else {
+                reset_temp(state, vals, args[0], nb_temps, nb_globals);
+                gen_args[0] = args[0];
+                gen_args[1] = args[1];
+                gen_args[2] = args[2];
+                gen_args += 3;
+                args += 3;
+                break;
+            }
         case INDEX_op_call:
         case INDEX_op_jmp:
         case INDEX_op_br:
-- 
1.7.4.1