From: Kito Cheng <kito.cheng@sifive.com>
To: "Christoph Müllner" <christoph.muellner@vrull.eu>
Cc: Palmer Dabbelt <palmer@dabbelt.com>,
adhemerval.zanella@linaro.org, libc-alpha@sourceware.org,
Darius Rad <darius@bluespec.com>,
Andrew Waterman <andrew@sifive.com>,
philipp.tomsich@vrull.eu, Evan Green <evan@rivosinc.com>,
DJ Delorie <dj@redhat.com>, Vineet Gupta <vineetg@rivosinc.com>,
jeffreyalaw@gmail.com
Subject: Re: [PATCH 2/7] RISC-V: Add Zbb optimized memchr as ifunc
Date: Mon, 6 May 2024 21:58:17 +0800 [thread overview]
Message-ID: <CALLt3TjoaoH=B03DKmWmo0MpG-tbNJZHunkkMhuyHNr2yrvWAA@mail.gmail.com> (raw)
In-Reply-To: <CAEg0e7h7fV-1HkWXVfrt1CiDK7O4aXcnfTbqFZpYFdgWniZM1A@mail.gmail.com>
> > `target` attribute is provided by GCC 14, and `-march=+ext` will at
> > least require GCC 15 (if we add),
> > also we relaxed the canonical order requirement for `-march=`, that
> > means we can relatively easy to manipulate the ISA
> > string by just concat that? so I don't really think we need `-march=+ext`.
>
> Then we require the Makefile author to:
> 1) parse if the current compiler flags include march (repeat for all
> variables that may be used)
> 2a) if so, then amend to that
> 2b) if not, parse if there is a configured default ISA (via "gcc -v")
> 2ba) if so, then create -march accordingly
> 2bb) if not, then <fail to amend>
>
> Bonus problem:
> If there are multiple variables that might set -march=... this gets
> even trickier because
> the order how these variables are integrated in the compiler
> invocation command is unknown.
>
> Using "-march=+zfoo" seems simpler and cleaner.
I agree it will require the compiler to parse the gcc -v to obtain the
default -march, it might be a burden,
but AArch64 also does not allow -march=+ext only it requires
-march=arch{+[no]feature}*,
so I am wondering why do we need that to resolve/improve ifunc
implementation but not `target` attribute and `.option arch, +ext`?
next prev parent reply other threads:[~2024-05-06 13:58 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-22 7:43 [PATCH 0/7] Add ifunc support for existing Zbb optimizations Christoph Müllner
2024-04-22 7:43 ` [PATCH 1/7] RISC-V: Use .insn directive form for orc.b Christoph Müllner
2024-04-22 7:43 ` [PATCH 2/7] RISC-V: Add Zbb optimized memchr as ifunc Christoph Müllner
2024-04-24 12:53 ` Adhemerval Zanella Netto
2024-04-24 13:16 ` Christoph Müllner
2024-04-24 13:36 ` Adhemerval Zanella Netto
2024-04-26 11:40 ` Christoph Müllner
2024-04-30 15:13 ` Palmer Dabbelt
2024-04-30 17:45 ` Adhemerval Zanella Netto
2024-04-30 17:54 ` Palmer Dabbelt
2024-04-30 18:44 ` Vineet Gupta
2024-05-06 13:20 ` Christoph Müllner
2024-05-06 13:32 ` Kito Cheng
2024-05-06 13:46 ` Christoph Müllner
2024-05-06 13:58 ` Kito Cheng [this message]
2024-04-22 7:43 ` [PATCH 3/7] RISC-V: Add Zbb optimized memrchr " Christoph Müllner
2024-04-22 7:44 ` [PATCH 4/7] RISC-V: Add Zbb optimized strchrnul " Christoph Müllner
2024-04-22 7:44 ` [PATCH 5/7] RISC-V: Add Zbb optimized strcmp " Christoph Müllner
2024-04-22 7:44 ` [PATCH 6/7] RISC-V: Add Zbb optimized strlen " Christoph Müllner
2024-04-22 7:44 ` [PATCH 7/7] RISC-V: Add Zbb optimized strncmp " Christoph Müllner
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