[Qemu-devel] [PATCH 2/9] tcg/optimizer: check types in copy propagation

[Aurelien Jarno]

The copy propagation doesn't check the types of the temps during copy
propagation. However TCG is using the mov_i32 for the i64 to i32
conversion and thus the two are not equivalent.

With this patch tcg_opt_gen_mov() doesn't consider two temps with
different types as copies anymore.

So far it seems the optimization was not aggressive enough to trigger
this bug, but it will be triggered later in this series once the copy
propagation is improved.

Signed-off-by: Aurelien Jarno <address@hidden>
---
 tcg/optimize.c |   18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/tcg/optimize.c b/tcg/optimize.c
index ca81198..13b5b15 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -106,12 +106,13 @@ static TCGOpcode op_to_movi(TCGOpcode op)
     }
 }
 
-static void tcg_opt_gen_mov(TCGArg *gen_args, TCGArg dst, TCGArg src,
-                            int nb_temps, int nb_globals)
+static void tcg_opt_gen_mov(TCGContext *s, TCGArg *gen_args,
+                            TCGArg dst, TCGArg src)
 {
-        reset_temp(dst, nb_temps, nb_globals);
+        reset_temp(dst, s->nb_temps, s->nb_globals);
         assert(temps[src].state != TCG_TEMP_COPY);
-        if (src >= nb_globals) {
+        /* Only consider temps with the same type (width) as copies. */
+        if (src >= s->nb_globals && s->temps[dst].type == s->temps[src].type) {
             assert(temps[src].state != TCG_TEMP_CONST);
             if (temps[src].state != TCG_TEMP_HAS_COPY) {
                 temps[src].state = TCG_TEMP_HAS_COPY;
@@ -440,8 +441,7 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t 
*tcg_opc_ptr,
                     gen_opc_buf[op_index] = INDEX_op_nop;
                 } else {
                     gen_opc_buf[op_index] = op_to_mov(op);
-                    tcg_opt_gen_mov(gen_args, args[0], args[1],
-                                    nb_temps, nb_globals);
+                    tcg_opt_gen_mov(s, gen_args, args[0], args[1]);
                     gen_args += 2;
                 }
                 args += 3;
@@ -478,8 +478,7 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t 
*tcg_opc_ptr,
                     gen_opc_buf[op_index] = INDEX_op_nop;
                 } else {
                     gen_opc_buf[op_index] = op_to_mov(op);
-                    tcg_opt_gen_mov(gen_args, args[0], args[1], nb_temps,
-                                    nb_globals);
+                    tcg_opt_gen_mov(s, gen_args, args[0], args[1]);
                     gen_args += 2;
                 }
                 args += 3;
@@ -503,8 +502,7 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t 
*tcg_opc_ptr,
                 break;
             }
             if (temps[args[1]].state != TCG_TEMP_CONST) {
-                tcg_opt_gen_mov(gen_args, args[0], args[1],
-                                nb_temps, nb_globals);
+                tcg_opt_gen_mov(s, gen_args, args[0], args[1]);
                 gen_args += 2;
                 args += 2;
                 break;
-- 
1.7.10.4