diff mbox series

[v4,13/23] target/arm: Improve gen_top_byte_ignore

Message ID 20210128224141.638790-14-richard.henderson@linaro.org (mailing list archive)
State New, archived
Headers show
Series target-arm: Implement ARMv8.5-MemTag, user mode | expand

Commit Message

Richard Henderson Jan. 28, 2021, 10:41 p.m. UTC 
Use simple arithmetic instead of a conditional
move when tbi0 != tbi1.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/arm/translate-a64.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

Comments

Peter Maydell Feb. 2, 2021, 2:40 p.m. UTC | #1 
On Thu, 28 Jan 2021 at 22:42, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> Use simple arithmetic instead of a conditional
> move when tbi0 != tbi1.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/arm/translate-a64.c | 25 ++++++++++++++-----------
>  1 file changed, 14 insertions(+), 11 deletions(-)

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM
diff mbox series

Patch

diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
index ffc060e5d7..3ec0dc17d8 100644
--- a/target/arm/translate-a64.c
+++ b/target/arm/translate-a64.c
@@ -183,17 +183,20 @@  static void gen_top_byte_ignore(DisasContext *s, TCGv_i64 dst,
         /* Sign-extend from bit 55.  */
         tcg_gen_sextract_i64(dst, src, 0, 56);
 
-        if (tbi != 3) {
-            TCGv_i64 tcg_zero = tcg_const_i64(0);
-
-            /*
-             * The two TBI bits differ.
-             * If tbi0, then !tbi1: only use the extension if positive.
-             * if !tbi0, then tbi1: only use the extension if negative.
-             */
-            tcg_gen_movcond_i64(tbi == 1 ? TCG_COND_GE : TCG_COND_LT,
-                                dst, dst, tcg_zero, dst, src);
-            tcg_temp_free_i64(tcg_zero);
+        switch (tbi) {
+        case 1:
+            /* tbi0 but !tbi1: only use the extension if positive */
+            tcg_gen_and_i64(dst, dst, src);
+            break;
+        case 2:
+            /* !tbi0 but tbi1: only use the extension if negative */
+            tcg_gen_or_i64(dst, dst, src);
+            break;
+        case 3:
+            /* tbi0 and tbi1: always use the extension */
+            break;
+        default:
+            g_assert_not_reached();
         }
     }
 }