On Wed, 25 Oct 2023 16:41:07 +0530
Ajit Agarwal <aagar...@linux.ibm.com> wrote:
> On 25/10/23 2:19 am, Vineet Gupta wrote:
> > On 10/24/23 13:36, rep.dot....@gmail.com wrote:
> >>>>>> As said, I don't see why the below was not cleaned up before the V1
> >>>>>> submission.
> >>>>>> Iff it breaks when manually CSEing, I'm curious why?
> >>>> The function below looks identical in v12 of the patch.
> >>>> Why didn't you use common subexpressions?
> >>>> ba
> >>> Using CSE here breaks aarch64 regressions hence I have reverted it back
> >>> not to use CSE,
> >> Just for my own education, can you please paste your patch perusing common
> >> subexpressions and an assembly diff of the failing versus working aarch64
> >> testcase, along how you configured that failing (cross-?)compiler and the
> >> command-line of a typical testcase that broke when manually CSEing the
> >> function below?
> >
> > I was meaning to ask this before, but what exactly is the CSE issue,
> > manually or whatever.
If nothing else it would hopefully improve the readability.
> >
> Here is the abi interface where I CSE'D and got a mail from automated
> regressions run that aarch64
> test fails.
We already concluded that this failure was obviously a hiccup on the
testers, no problem.
> +static inline bool
> +abi_extension_candidate_return_reg_p (int regno)
> +{
> + return targetm.calls.function_value_regno_p (regno);
> +}
But i was referring to abi_extension_candidate_p :)
your v13 looks like this:
+static bool
+abi_extension_candidate_p (rtx_insn *insn)
+{
+ rtx set = single_set (insn);
+ machine_mode dst_mode = GET_MODE (SET_DEST (set));
+ rtx orig_src = XEXP (SET_SRC (set), 0);
+
+ if (!FUNCTION_ARG_REGNO_P (REGNO (orig_src))
+ || abi_extension_candidate_return_reg_p (REGNO (orig_src)))
+ return false;
+
+ /* Return FALSE if mode of destination and source is same. */
+ if (dst_mode == GET_MODE (orig_src))
+ return false;
+
+ machine_mode mode = GET_MODE (XEXP (SET_SRC (set), 0));
+ bool promote_p = abi_target_promote_function_mode (mode);
+
+ /* Return FALSE if promote is false and REGNO of source and destination
+ is different. */
+ if (!promote_p && REGNO (SET_DEST (set)) != REGNO (orig_src))
+ return false;
+
+ return true;
+}
and i suppose it would be easier to read if phrased something like
static bool
abi_extension_candidate_p (rtx_insn *insn)
{
rtx set = single_set (insn);
rtx orig_src = XEXP (SET_SRC (set), 0);
unsigned int src_regno = REGNO (orig_src);
/* Not a function argument reg or is a function values return reg. */
if (!FUNCTION_ARG_REGNO_P (src_regno)
|| abi_extension_candidate_return_reg_p (src_regno))
return false;
rtx dst = SET_DST (set);
machine_mode src_mode = GET_MODE (orig_src);
/* Return FALSE if mode of destination and source is the same. */
if (GET_MODE (dst) == src_mode)
return false;
/* Return FALSE if the FIX THE COMMENT and REGNO of source and destination
is different. */
if (!abi_target_promote_function_mode_p (src_mode)
&& REGNO (dst) != src_regno)
return false;
return true;
}
so no, that's not exactly better.
Maybe just do what the function comment says (i did not check the "not
promoted" part, but you get the idea):
^L
/* Return TRUE if
reg source operand is argument register and not return register,
mode of source and destination operand are different,
if not promoted REGNO of source and destination operand are the same. */
static bool
abi_extension_candidate_p (rtx_insn *insn)
{
rtx set = single_set (insn);
rtx orig_src = XEXP (SET_SRC (set), 0);
if (FUNCTION_ARG_REGNO_P (REGNO (orig_src))
&& !abi_extension_candidate_return_reg_p (REGNO (orig_src))
&& GET_MODE (SET_DST (set)) != GET_MODE (orig_src)
&& abi_target_promote_function_mode_p (GET_MODE (orig_src))
&& REGNO (SET_DST (set)) == REGNO (orig_src))
return true;
return false;
}
I think this is much easier to actually read (and that's why good
function comments are important). In the end it's not important and
just personal preference.
Either way, I did not check the plausibility of the logic therein.
>
>
> I have not done any assembly diff as myself have not cross compiled with
> aarch64.
fair enough.
