Re: [PATCH v3 15/38] target/s390x: Improve general case of disas_jcc

[Philippe Mathieu-Daudé]

Hi Richard,

On 10/1/24 23:43, Richard Henderson wrote:

Avoid code duplication by handling 7 of the 14 cases
by inverting the test for the other 7 cases.

Use TCG_COND_TSTNE for cc in {1,3}.
Use (cc - 1) <= 1 for cc in {1,2}.

Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
  target/s390x/tcg/translate.c | 82 +++++++++++++-----------------------
  1 file changed, 30 insertions(+), 52 deletions(-)

diff --git a/target/s390x/tcg/translate.c b/target/s390x/tcg/translate.c
index ae4e7b27ec..168974f2e6 100644
--- a/target/s390x/tcg/translate.c
+++ b/target/s390x/tcg/translate.c
@@ -885,67 +885,45 @@ static void disas_jcc(DisasContext *s, DisasCompare *c, 
uint32_t mask)
      case CC_OP_STATIC:
          c->is_64 = false;
          c->u.s32.a = cc_op;
-        switch (mask) {
-        case 0x8 | 0x4 | 0x2: /* cc != 3 */
-            cond = TCG_COND_NE;
+
+        /* Fold half of the cases using bit 3 to invert. */
+        switch (mask & 8 ? mask ^ 0xf : mask) {
+        case 0x1: /* cc == 3 */
+            cond = TCG_COND_EQ;
              c->u.s32.b = tcg_constant_i32(3);
              break;
-        case 0x8 | 0x4 | 0x1: /* cc != 2 */
-            cond = TCG_COND_NE;
-            c->u.s32.b = tcg_constant_i32(2);
-            break;
-        case 0x8 | 0x2 | 0x1: /* cc != 1 */
-            cond = TCG_COND_NE;
-            c->u.s32.b = tcg_constant_i32(1);
-            break;
-        case 0x8 | 0x2: /* cc == 0 || cc == 2 => (cc & 1) == 0 */
-            cond = TCG_COND_EQ;
-            c->u.s32.a = tcg_temp_new_i32();
-            c->u.s32.b = tcg_constant_i32(0);
-            tcg_gen_andi_i32(c->u.s32.a, cc_op, 1);
-            break;
-        case 0x8 | 0x4: /* cc < 2 */
-            cond = TCG_COND_LTU;
-            c->u.s32.b = tcg_constant_i32(2);
-            break;
-        case 0x8: /* cc == 0 */
-            cond = TCG_COND_EQ;
-            c->u.s32.b = tcg_constant_i32(0);
-            break;
-        case 0x4 | 0x2 | 0x1: /* cc != 0 */
-            cond = TCG_COND_NE;
-            c->u.s32.b = tcg_constant_i32(0);
-            break;
-        case 0x4 | 0x1: /* cc == 1 || cc == 3 => (cc & 1) != 0 */
-            cond = TCG_COND_NE;
-            c->u.s32.a = tcg_temp_new_i32();
-            c->u.s32.b = tcg_constant_i32(0);
-            tcg_gen_andi_i32(c->u.s32.a, cc_op, 1);
-            break;
-        case 0x4: /* cc == 1 */
-            cond = TCG_COND_EQ;
-            c->u.s32.b = tcg_constant_i32(1);
-            break;
-        case 0x2 | 0x1: /* cc > 1 */
-            cond = TCG_COND_GTU;
-            c->u.s32.b = tcg_constant_i32(1);
-            break;
          case 0x2: /* cc == 2 */
              cond = TCG_COND_EQ;
              c->u.s32.b = tcg_constant_i32(2);
              break;
-        case 0x1: /* cc == 3 */
+        case 0x4: /* cc == 1 */
              cond = TCG_COND_EQ;
-            c->u.s32.b = tcg_constant_i32(3);
+            c->u.s32.b = tcg_constant_i32(1);
+            break;
+        case 0x2 | 0x1: /* cc == 2 || cc == 3 => cc > 1 */
+            cond = TCG_COND_GTU;
+            c->u.s32.b = tcg_constant_i32(1);
+            break;
+        case 0x4 | 0x1: /* cc == 1 || cc == 3 => (cc & 1) != 0 */
+            cond = TCG_COND_TSTNE;
+            c->u.s32.b = tcg_constant_i32(1);

Don't we need to AND?

              c->u.s32.a = tcg_temp_new_i32();
              tcg_gen_andi_i32(c->u.s32.a, cc_op, 1);

+            break;
+        case 0x4 | 0x2: /* cc == 1 || cc == 2 => (cc - 1) <= 1 */
+            cond = TCG_COND_LEU;
+            c->u.s32.a = tcg_temp_new_i32();
+            c->u.s32.b = tcg_constant_i32(1);
+            tcg_gen_addi_i32(c->u.s32.a, cc_op, -1);
+            break;
+        case 0x4 | 0x2 | 0x1: /* cc != 0 */
+            cond = TCG_COND_NE;
+            c->u.s32.b = tcg_constant_i32(0);
              break;
          default:
-            /* CC is masked by something else: (8 >> cc) & mask.  */
-            cond = TCG_COND_NE;
-            c->u.s32.a = tcg_temp_new_i32();
-            c->u.s32.b = tcg_constant_i32(0);
-            tcg_gen_shr_i32(c->u.s32.a, tcg_constant_i32(8), cc_op);
-            tcg_gen_andi_i32(c->u.s32.a, c->u.s32.a, mask);
-            break;
+            /* case 0: never, handled above. */
+            g_assert_not_reached();
+        }
+        if (mask & 8) {
+            cond = tcg_invert_cond(cond);
          }
          break;