Hexagon (target/hexagon) decide if pred has been written at TCG gen time

Multiple writes to the same preg are and'ed together.  Rather than
generating a runtime check, we can determine at TCG generation time
if the predicate has previously been written in the packet.

Test added to tests/tcg/hexagon/misc.c

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <1617930474-31979-7-git-send-email-tsimpson@quicinc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 15 insertions, 7 deletions

diff --git a/target/hexagon/genptr.c b/target/hexagon/genptr.c
index 07d970fc6c..6b74344795 100644
--- a/target/hexagon/genptr.c
+++ b/target/hexagon/genptr.c
@@ -119,20 +119,28 @@ static void gen_log_reg_write_pair(int rnum, TCGv_i64 val)
 #endif
 }
 
-static inline void gen_log_pred_write(int pnum, TCGv val)
+static inline void gen_log_pred_write(DisasContext *ctx, int pnum, TCGv val)
 {
     TCGv zero = tcg_const_tl(0);
     TCGv base_val = tcg_temp_new();
     TCGv and_val = tcg_temp_new();
     TCGv pred_written = tcg_temp_new();
 
-    /* Multiple writes to the same preg are and'ed together */
     tcg_gen_andi_tl(base_val, val, 0xff);
-    tcg_gen_and_tl(and_val, base_val, hex_new_pred_value[pnum]);
-    tcg_gen_andi_tl(pred_written, hex_pred_written, 1 << pnum);
-    tcg_gen_movcond_tl(TCG_COND_NE, hex_new_pred_value[pnum],
-                       pred_written, zero,
-                       and_val, base_val);
+
+    /*
+     * Section 6.1.3 of the Hexagon V67 Programmer's Reference Manual
+     *
+     * Multiple writes to the same preg are and'ed together
+     * If this is the first predicate write in the packet, do a
+     * straight assignment.  Otherwise, do an and.
+     */
+    if (!test_bit(pnum, ctx->pregs_written)) {
+        tcg_gen_mov_tl(hex_new_pred_value[pnum], base_val);
+    } else {
+        tcg_gen_and_tl(hex_new_pred_value[pnum],
+                       hex_new_pred_value[pnum], base_val);
+    }
     tcg_gen_ori_tl(hex_pred_written, hex_pred_written, 1 << pnum);
 
     tcg_temp_free(zero);