[binutils-gdb] gdb: LoongArch: Implement the return_value gdbarch method

[Tiezhu Yang <yangtiezhu@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=0b8c95579f78b352cd48cc14e48ea842c64a7a5a

commit 0b8c95579f78b352cd48cc14e48ea842c64a7a5a
Author: Tiezhu Yang <yangtiezhu@loongson.cn>
Date:   Mon May 9 16:26:47 2022 +0800

    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>

Diff:
---
 gdb/loongarch-tdep.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/gdb/loongarch-tdep.c b/gdb/loongarch-tdep.c
index e30ef8084da..28f04094f64 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);