From: Jeff Law <jeffreyalaw@gmail.com>
To: Kito Cheng <kito.cheng@gmail.com>, yanzhang.wang@intel.com
Cc: gcc-patches@gcc.gnu.org, juzhe.zhong@rivai.ai,
kito.cheng@sifive.com, pan2.li@intel.com
Subject: Re: [PATCH v3] RISCV: Add -m(no)-omit-leaf-frame-pointer support.
Date: Thu, 20 Jul 2023 22:11:10 -0600 [thread overview]
Message-ID: <392d76fe-b3cd-f86d-c7d8-188149ca3e79@gmail.com> (raw)
In-Reply-To: <CA+yXCZBeThy57v930V7W70EPz-Z7vSXUayJ-q6-0FOcXBPc6Qg@mail.gmail.com>
On 7/20/23 21:49, Kito Cheng wrote:
> LGTM, I think long jump is another issue and making ra become a fixed
> register will escalate to an ABI issue, so that should not be a
> blocker for this patch.
I'll take a look tomorrow, but I'm supportive of what Yanzhang is trying
to do in principle. I've got a few hot items to deal with tonight though.
WRT making $ra fixed. In practice fixing a register just takes it out
of the pool of things available to the allocator. Furthermore $ra is
always considered clobbered at call sites. So while one could view it
as an ABI change, it's not one that's actually observable in practice.
I suspect that's one of the reasons why $ra is used by the assembler in
this manner -- it minimizes both the ABI and performance impacts.
jeff
next prev parent reply other threads:[~2023-07-21 4:11 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-02 7:07 [PATCH] " yanzhang.wang
2023-06-03 2:43 ` Jeff Law
2023-06-05 2:49 ` Wang, Yanzhang
2023-06-07 2:13 ` Jeff Law
2023-06-07 3:50 ` Wang, Yanzhang
2023-06-08 15:05 ` Jeff Law
2023-06-21 8:14 ` Wang, Yanzhang
2023-06-24 15:01 ` Jeff Law
2023-06-25 1:40 ` Stefan O'Rear
2023-06-25 12:49 ` Jeff Law
2023-06-25 18:45 ` Stefan O'Rear
2023-06-26 14:30 ` Jeff Law
2023-06-26 14:50 ` Kito Cheng
2023-06-26 16:51 ` Jeff Law
2023-06-05 1:04 ` Li, Pan2
2023-06-05 3:36 ` Wang, Yanzhang
2023-07-13 6:12 ` yanzhang.wang
2023-07-18 7:49 ` [PATCH v3] " yanzhang.wang
2023-07-21 3:49 ` Kito Cheng
2023-07-21 4:11 ` Jeff Law [this message]
2023-08-02 1:51 ` Wang, Yanzhang
2023-08-03 6:12 ` Jeff Law
2023-08-03 6:16 ` Li, Pan2
2023-08-03 6:22 ` Li, Pan2
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