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>

2 files changed, 29 insertions, 3 deletions

diff --git a/target/hexagon/gen_trans_funcs.py b/target/hexagon/gen_trans_funcs.py
index 9f86b4e..30f0c73 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"
 
diff --git a/tests/tcg/hexagon/hvx_misc.c b/tests/tcg/hexagon/hvx_misc.c
index 1fe14b5..90c3733 100644
--- a/tests/tcg/hexagon/hvx_misc.c
+++ b/tests/tcg/hexagon/hvx_misc.c
@@ -474,6 +474,27 @@ static void test_vcombine(void)
     check_output_w(__LINE__, BUFSIZE);
 }
 
+void test_store_new()
+{
+    asm volatile(
+        "r0 = #0x12345678\n"
+        "v0 = vsplat(r0)\n"
+        "r0 = #0xff00ff00\n"
+        "v1 = vsplat(r0)\n"
+        "{\n"
+        "   vdeal(v1,v0,r0)\n"
+        "   vmem(%0) = v0.new\n"
+        "}\n"
+        :
+        : "r"(&output[0])
+        : "r0", "v0", "v1", "memory"
+    );
+    for (int i = 0; i < MAX_VEC_SIZE_BYTES / 4; i++) {
+        expect[0].w[i] = 0x12345678;
+    }
+    check_output_w(__LINE__, 1);
+}
+
 int main()
 {
     init_buffers();
@@ -515,6 +536,8 @@ int main()
 
     test_vcombine();
 
+    test_store_new();
+
     puts(err ? "FAIL" : "PASS");
     return err ? 1 : 0;
 }