[PATCH] gdb: mips: Fix the handling of complex type of function return value

Youling Tang
2022-03-16T04:48:42Z

$ objdump -d outputs/gdb.base/varargs/varargs
00000001200012e8 <find_max_float_real>:
...
1200013b8: c7c10000 lwc1 $f1,0(s8)
1200013bc: c7c00004 lwc1 $f0,4(s8)
1200013c0: 46000886 mov.s $f2,$f1
1200013c4: 46000046 mov.s $f1,$f0
1200013c8: 46001006 mov.s $f0,$f2
1200013cc: 46000886 mov.s $f2,$f1
1200013d0: 03c0e825 move sp,s8
1200013d4: dfbe0038 ld s8,56(sp)
1200013d8: 67bd0080 daddiu sp,sp,128
1200013dc: 03e00008 jr ra
1200013e0: 00000000 nop

From the above disassembly, we can see that when the return value of the
function is a complex type and len <= 2 * MIPS64_REGSIZE, the return value
will be passed through $f0 and $f2, so fix the corresponding processing
in mips_n32n64_return_value().

$ make check RUNTESTFLAGS='GDB=../gdb gdb.base/varargs.exp --outdir=test'

Before applying the patch:
FAIL: gdb.base/varargs.exp: print find_max_float_real(4, fc1, fc2, fc3, fc4)
FAIL: gdb.base/varargs.exp: print find_max_double_real(4, dc1, dc2, dc3, dc4)

# of expected passes 9
# of unexpected failures 2

After applying the patch:
# of expected passes 11

Signed-off-by: Youling Tang <tangyouling@loongson.cn>
---
gdb/mips-tdep.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gdb/mips-tdep.c b/gdb/mips-tdep.c
index 7e37578..cddb8f8 100644
--- a/gdb/mips-tdep.c
+++ b/gdb/mips-tdep.c
@@ -5224,9 +5224,10 @@ mips_n32n64_return_value (struct gdbarch *gdbarch, struct value *function,

if (TYPE_LENGTH (type) > 2 * MIPS64_REGSIZE)
return RETURN_VALUE_STRUCT_CONVENTION;
- else if (type->code () == TYPE_CODE_FLT
+ else if ((type->code () == TYPE_CODE_FLT
&& TYPE_LENGTH (type) == 16
&& tdep->mips_fpu_type != MIPS_FPU_NONE)
+ || (type->code () == TYPE_CODE_COMPLEX))
{
/* A 128-bit floating-point value fills both $f0 and $f2. The
two registers are used in the same as memory order, so the
--
2.1.0