[2/2] RISC-V: NaN-box FP values smaller than an FP register.
Commit Message
The hardware requires that values in FP registers be NaN-boxed, so we must
extend them with 1's instead of 0's as we do for integer values.
gdb/
* riscv-tdep.c (riscv_push_dummy_call) <in_reg>: Check for value in
FP reg smaller than FP reg size, and fill with -1 instead of 0.
---
gdb/riscv-tdep.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
Comments
On Fri, 19 Oct 2018 14:49:53 -0700
Jim Wilson <jimw@sifive.com> wrote:
> The hardware requires that values in FP registers be NaN-boxed, so we must
> extend them with 1's instead of 0's as we do for integer values.
>
> gdb/
> * riscv-tdep.c (riscv_push_dummy_call) <in_reg>: Check for value in
> FP reg smaller than FP reg size, and fill with -1 instead of 0.
Okay.
Kevin
On Sat, Oct 20, 2018 at 2:39 PM Kevin Buettner <kevinb@redhat.com> wrote:
> On Fri, 19 Oct 2018 14:49:53 -0700
> Jim Wilson <jimw@sifive.com> wrote:
>
> > The hardware requires that values in FP registers be NaN-boxed, so we must
> > extend them with 1's instead of 0's as we do for integer values.
> >
> > gdb/
> > * riscv-tdep.c (riscv_push_dummy_call) <in_reg>: Check for value in
> > FP reg smaller than FP reg size, and fill with -1 instead of 0.
>
> Okay.
Committed.
Jim
@@ -2408,7 +2408,12 @@ riscv_push_dummy_call (struct gdbarch *gdbarch,
gdb_byte tmp [sizeof (ULONGEST)];
gdb_assert (info->argloc[0].c_length <= info->length);
- memset (tmp, 0, sizeof (tmp));
+ /* FP values in FP registers must be NaN-boxed. */
+ if (riscv_is_fp_regno_p (info->argloc[0].loc_data.regno)
+ && info->argloc[0].c_length < call_info.flen)
+ memset (tmp, -1, sizeof (tmp));
+ else
+ memset (tmp, 0, sizeof (tmp));
memcpy (tmp, info->contents, info->argloc[0].c_length);
regcache->cooked_write (info->argloc[0].loc_data.regno, tmp);
second_arg_length =
@@ -2447,7 +2452,12 @@ riscv_push_dummy_call (struct gdbarch *gdbarch,
gdb_assert ((riscv_is_fp_regno_p (info->argloc[1].loc_data.regno)
&& second_arg_length <= call_info.flen)
|| second_arg_length <= call_info.xlen);
- memset (tmp, 0, sizeof (tmp));
+ /* FP values in FP registers must be NaN-boxed. */
+ if (riscv_is_fp_regno_p (info->argloc[1].loc_data.regno)
+ && second_arg_length < call_info.flen)
+ memset (tmp, -1, sizeof (tmp));
+ else
+ memset (tmp, 0, sizeof (tmp));
memcpy (tmp, second_arg_data, second_arg_length);
regcache->cooked_write (info->argloc[1].loc_data.regno, tmp);
}