Hexagon: fix HVX store new

At 09a7e7db0f (Hexagon (target/hexagon) Remove uses of
op_regs_generated.h.inc, 2024-03-06), we've changed the logic of
check_new_value() to use the new pre-calculated
packet->insn[...].dest_idx instead of calculating the index on the fly
using opcode_reginfo[...]. The dest_idx index is calculated roughly like
the following:

    for reg in iset[tag]["syntax"]:
        if reg.is_written():
            dest_idx = regno
            break

Thus, we take the first register that is writtable. Before that,
however, we also used to follow an alphabetical order on the register
type: 'd', 'e', 'x', and 'y'. No longer following that makes us select
the wrong register index and the HVX store new instruction does not
update the memory like expected.

Signed-off-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
Reviewed-by: Brian Cain <bcain@quicinc.com>
Reviewed-by: Taylor Simpson <ltaylorsimpson@gmail.com>
Message-Id: <f548dc1c240819c724245e887f29f918441e9125.1716220379.git.quic_mathbern@quicinc.com>
Signed-off-by: Brian Cain <bcain@quicinc.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/target/hexagon/gen_trans_funcs.py b/target/hexagon/gen_trans_funcs.py
index 9f86b4edbd..30f0c73e0c 100755
--- a/target/hexagon/gen_trans_funcs.py
+++ b/target/hexagon/gen_trans_funcs.py
@@ -89,6 +89,7 @@ def gen_trans_funcs(f):
 
         new_read_idx = -1
         dest_idx = -1
+        dest_idx_reg_id = None
         has_pred_dest = "false"
         for regno, (reg_type, reg_id, *_) in enumerate(regs):
             reg = hex_common.get_register(tag, reg_type, reg_id)
@@ -97,9 +98,11 @@ def gen_trans_funcs(f):
             """))
             if reg.is_read() and reg.is_new():
                 new_read_idx = regno
-            # dest_idx should be the first destination, so check for -1
-            if reg.is_written() and dest_idx == -1:
-                dest_idx = regno
+            if reg.is_written():
+                # dest_idx should be the first destination alphabetically
+                if dest_idx_reg_id is None or reg_id < dest_idx_reg_id:
+                    dest_idx = regno
+                    dest_idx_reg_id = reg_id
             if reg_type == "P" and reg.is_written() and not reg.is_read():
                 has_pred_dest = "true"