[Qemu-devel] [PATCH 02/12] target-arm: optimize thumb 32bit multiply

[Juha.Riihimaki]

Current implementation of thumb mul instruction is implemented as a  
32x32->64 multiply which then uses only 32 least significant bits of  
the result. Replace that with a simple 32x32->32 multiply.

Signed-off-by: Juha Riihimäki <address@hidden>
---
diff --git a/target-arm/translate.c b/target-arm/translate.c
index bda105e..3ea9d51 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -310,22 +310,6 @@ static TCGv_i64 gen_muls_i64_i32(TCGv a, TCGv b)
      return tmp1;
  }

-/* Unsigned 32x32->64 multiply.  */
-static void gen_mull(TCGv a, TCGv b)
-{
-    TCGv_i64 tmp1 = tcg_temp_new_i64();
-    TCGv_i64 tmp2 = tcg_temp_new_i64();
-
-    tcg_gen_extu_i32_i64(tmp1, a);
-    tcg_gen_extu_i32_i64(tmp2, b);
-    tcg_gen_mul_i64(tmp1, tmp1, tmp2);
-    tcg_temp_free_i64(tmp2);
-    tcg_gen_trunc_i64_i32(a, tmp1);
-    tcg_gen_shri_i64(tmp1, tmp1, 32);
-    tcg_gen_trunc_i64_i32(b, tmp1);
-    tcg_temp_free_i64(tmp1);
-}
-
  /* Signed 32x32->64 multiply.  */
  static void gen_imull(TCGv a, TCGv b)
  {
@@ -8358,7 +8342,7 @@ static void disas_thumb_insn(CPUState *env,  
DisasContext *s)
                  gen_logic_CC(tmp);
              break;
          case 0xd: /* mul */
-            gen_mull(tmp, tmp2);
+            tcg_gen_mul_i32(tmp, tmp, tmp2);
              if (!s->condexec_mask)
                  gen_logic_CC(tmp);
              break;

translate.c.genmull.diff
Description: translate.c.genmull.diff