From: Jeff Law <jeffreyalaw@gmail.com>
To: Ajit Agarwal <aagarwa1@linux.ibm.com>,
Hans-Peter Nilsson <hp@bitrange.com>
Cc: gcc-patches <gcc-patches@gcc.gnu.org>,
Segher Boessenkool <segher@kernel.crashing.org>,
Peter Bergner <bergner@linux.ibm.com>,
Richard Biener <richard.guenther@gmail.com>
Subject: Re: [PATCH v4 4/4] ree: Improve ree pass for rs6000 target using defined ABI interfaces.
Date: Fri, 19 May 2023 13:32:49 -0600 [thread overview]
Message-ID: <18f2005d-3f59-1c3f-b1e4-97572416441e@gmail.com> (raw)
In-Reply-To: <438860a6-4c03-2d5b-c465-833998e80bab@linux.ibm.com>
On 5/16/23 06:35, Ajit Agarwal wrote:
>
>
> On 29/04/23 5:03 am, Jeff Law wrote:
>>
>>
>> On 4/28/23 16:42, Hans-Peter Nilsson wrote:
>>> On Sat, 22 Apr 2023, Ajit Agarwal via Gcc-patches wrote:
>>>
>>>> Hello All:
>>>>
>>>> This new version of patch 4 use improve ree pass for rs6000 target using defined ABI interfaces.
>>>> Bootstrapped and regtested on power64-linux-gnu.
>>>>
>>>> Thanks & Regards
>>>> Ajit
>>>>
>>>>
>>>> ree: Improve ree pass for rs6000 target using defined abi interfaces
>>>>
>>>> For rs6000 target we see redundant zero and sign
>>>> extension and done to improve ree pass to eliminate
>>>> such redundant zero and sign extension using defines
>>>> ABI interfaces.
>>>>
>>>> 2023-04-22 Ajit Kumar Agarwal <aagarwa1@linux.ibm.com>
>>>>
>>>> gcc/ChangeLog:
>>>>
>>>> * ree.cc (combline_reaching_defs): Add zero_extend
>>>> using defined abi interfaces.
>>>> (add_removable_extension): use of defined abi interfaces
>>>> for no reaching defs.
>>>> (abi_extension_candidate_return_reg_p): New defined ABI function.
>>>> (abi_extension_candidate_p): New defined ABI function.
>>>> (abi_extension_candidate_argno_p): New defined ABI function.
>>>> (abi_handle_regs_without_defs_p): New defined ABI function.
>>>>
>>>> gcc/testsuite/ChangeLog:
>>>>
>>>> * g++.target/powerpc/zext-elim-3.C
>>>> ---
>>>> gcc/ree.cc | 176 +++++++++++++++---
>>>> .../g++.target/powerpc/zext-elim-3.C | 16 ++
>>>> 2 files changed, 162 insertions(+), 30 deletions(-)
>>>> create mode 100644 gcc/testsuite/g++.target/powerpc/zext-elim-3.C
>>>>
>>>> diff --git a/gcc/ree.cc b/gcc/ree.cc
>>>> index 413aec7c8eb..0de96b1ece1 100644
>>>> --- a/gcc/ree.cc
>>>> +++ b/gcc/ree.cc
>>>> @@ -473,7 +473,8 @@ get_defs (rtx_insn *insn, rtx reg, vec<rtx_insn *> *dest)
>>>> break;
>>>> }
>>>> - gcc_assert (use != NULL);
>>>> + if (use == NULL)
>>>> + return NULL;
>>>> ref_chain = DF_REF_CHAIN (use);
>>>> @@ -514,7 +515,8 @@ get_uses (rtx_insn *insn, rtx reg)
>>>> if (REGNO (DF_REF_REG (def)) == REGNO (reg))
>>>> break;
>>>> - gcc_assert (def != NULL);
>>>> + if (def == NULL)
>>>> + return NULL;
>>>> ref_chain = DF_REF_CHAIN (def);
>>>> @@ -750,6 +752,103 @@ get_extended_src_reg (rtx src)
>>>> return src;
>>>> }
>>>> +/* Return TRUE if the candidate insn is zero extend and regno is
>>>> + an return registers. */
>>>> +
>>>> +static bool
>>>> +abi_extension_candidate_return_reg_p (rtx_insn *insn, int regno)
>>>> +{
>>>> + rtx set = single_set (insn);
>>>> +
>>>> + if (GET_CODE (SET_SRC (set)) != ZERO_EXTEND)
>>>> + return false;
>>>> +
>>>> + if (FUNCTION_VALUE_REGNO_P (regno))
>>>> + return true;
>>>> +
>>>> + return false;
>>>> +}
>>>> +
>>>> +/* Return TRUE if reg source operand of zero_extend is argument registers
>>>> + and not return registers and source and destination operand are same
>>>> + and mode of source and destination operand are not same. */
>>>> +
>>>> +static bool
>>>> +abi_extension_candidate_p (rtx_insn *insn)
>>>> +{
>>>> + rtx set = single_set (insn);
>>>> +
>>>> + if (GET_CODE (SET_SRC (set)) != ZERO_EXTEND)
>>>> + return false;
>>>> +
>>>> + machine_mode ext_dst_mode = GET_MODE (SET_DEST (set));
>>>> + rtx orig_src = XEXP (SET_SRC (set),0);
>>>> +
>>>> + bool copy_needed
>>>> + = (REGNO (SET_DEST (set)) != REGNO (XEXP (SET_SRC (set), 0)));
>>>> +
>>>> + if (!copy_needed && ext_dst_mode != GET_MODE (orig_src)
>>>> + && FUNCTION_ARG_REGNO_P (REGNO (orig_src))
>>>> + && !abi_extension_candidate_return_reg_p (insn, REGNO (orig_src)))
>>>> + return true;
>>>> +
>>>> + return false;
>>>> +}
>>>> +
>>>> +/* Return TRUE if the candidate insn is zero extend and regno is
>>>> + an argument registers. */
>>>> +
>>>> +static bool
>>>> +abi_extension_candidate_argno_p (rtx_code code, int regno)
>>>> +{
>>>> + if (code != ZERO_EXTEND)
>>>> + return false;
>>>> +
>>>> + if (FUNCTION_ARG_REGNO_P (regno))
>>>> + return true;
>>>> +
>>>> + return false;
>>>> +}
>>>
>>> I don't see anything in those functions that checks if
>>> ZERO_EXTEND is actually a feature of the ABI, e.g. as opposed to
>>> no extension or SIGN_EXTEND. Do I miss something?
>> I don't think you missed anything. That was one of the points I was making last week. Somewhere, somehow we need to describe what the ABI mandates and guarantees.
>>
>> So while what Ajit has done is a step forward, at some point the actual details of the ABI need to be described in a way that can be checked and consumed by REE.
>
>
> The ABI we need for ree pass are the argument registers and return registers. Based on that I have described interfaces that we need. Other than that we dont any other ABI hooks. I have used FUNCTION_VALUE_REGNO_P and FuNCTION_ARG_REGNO_P abi hooks.
You're working with one of many ABIs, some of which have useful
properties, some of which do not.
Simply testing FUNCTION_VALUE_REGNO_P/FUNCTION_ARG_REGNO_P is not
sufficient. You need to be able to query the ABI properties.
jeff
next prev parent reply other threads:[~2023-05-19 19:32 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-22 9:06 Ajit Agarwal
2023-04-28 22:42 ` Hans-Peter Nilsson
2023-04-28 23:33 ` Jeff Law
2023-04-28 23:49 ` Hans-Peter Nilsson
2023-05-02 22:00 ` Peter Bergner
2023-05-16 12:35 ` Ajit Agarwal
2023-05-19 19:32 ` Jeff Law [this message]
2023-05-01 16:21 ` Segher Boessenkool
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