gdb: LoongArch: Implement the return_value gdbarch method

When execute the following command on LoongArch:

  make check-gdb TESTS="gdb.base/async.exp"

there exist the following failed testcases:

  FAIL: gdb.base/async.exp: finish& (timeout)
  FAIL: gdb.base/async.exp: jump& (timeout)
  FAIL: gdb.base/async.exp: until& (timeout)
  FAIL: gdb.base/async.exp: set exec-done-display off (GDB internal error)

we can see the following messages in gdb/testsuite/gdb.log:

  finish&
  Run till exit from #0  foo () at /home/loongson/gdb.git/gdb/testsuite/gdb.base/async.c:9
  (gdb) /home/loongson/gdb.git/gdb/gdbarch.c:2646: internal-error: gdbarch_return_value: Assertion `gdbarch->return_value != NULL' failed.
  A problem internal to GDB has been detected,
  further debugging may prove unreliable.

In order to fix the above failed testcases, implement the return_value
gdbarch method on LoongArch.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>

1 files changed, 33 insertions, 0 deletions

diff --git a/gdb/loongarch-tdep.c b/gdb/loongarch-tdep.c
index e30ef80..28f0409 100644
--- a/gdb/loongarch-tdep.c
+++ b/gdb/loongarch-tdep.c
@@ -247,6 +247,36 @@ static const struct frame_unwind loongarch_frame_unwind = {
   /*.prev_arch	   =*/nullptr,
 };
 
+/* Implement the return_value gdbarch method for LoongArch.  */
+
+static enum return_value_convention
+loongarch_return_value (struct gdbarch *gdbarch, struct value *function,
+			struct type *type, struct regcache *regcache,
+			gdb_byte *readbuf, const gdb_byte *writebuf)
+{
+  loongarch_gdbarch_tdep *tdep = (loongarch_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+  auto regs = tdep->regs;
+  int len = TYPE_LENGTH (type);
+  int regnum = -1;
+
+  /* See if our value is returned through a register.  If it is, then
+     store the associated register number in REGNUM.  */
+  switch (type->code ())
+    {
+      case TYPE_CODE_INT:
+	regnum = regs.r + 4;
+	break;
+    }
+
+  /* Extract the return value from the register where it was stored.  */
+  if (readbuf)
+    regcache->raw_read_part (regnum, 0, len, readbuf);
+  if (writebuf)
+    regcache->raw_write_part (regnum, 0, len, writebuf);
+
+  return RETURN_VALUE_REGISTER_CONVENTION;
+}
+
 /* Implement the "dwarf2_reg_to_regnum" gdbarch method.  */
 
 static int
@@ -418,6 +448,9 @@ loongarch_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   /* Finalise the target description registers.  */
   tdesc_use_registers (gdbarch, tdesc, std::move (tdesc_data));
 
+  /* Return value info  */
+  set_gdbarch_return_value (gdbarch, loongarch_return_value);
+
   /* Advance PC across function entry code.  */
   set_gdbarch_skip_prologue (gdbarch, loongarch_skip_prologue);