From: "Maciej W. Rozycki" <macro@orcam.me.uk>
To: Joseph Faulls <Joseph.Faulls@imgtec.com>
Cc: "binutils@sourceware.org" <binutils@sourceware.org>,
"palmer@rivosinc.com" <palmer@rivosinc.com>,
"nelson@rivosinc.com" <nelson@rivosinc.com>
Subject: Re: [PATCH] RISC-V: Do not gp relax against an ABS symbol if it is far away.
Date: Tue, 8 Aug 2023 10:49:23 +0100 (BST) [thread overview]
Message-ID: <alpine.DEB.2.21.2308080052050.38537@angie.orcam.me.uk> (raw)
In-Reply-To: <LO4P265MB59141A6F1238DFB73BC2A9818001A@LO4P265MB5914.GBRP265.PROD.OUTLOOK.COM>
On Thu, 27 Jul 2023, Joseph Faulls wrote:
> Relaxations can cause the gp to move after it has been decided to gp
> relax. Against an absolute symbol, the distance may change such that the
> offset can no longer fit in the 12-bit immediate field.
What's the use case for using AUIPC/LW to load an absolute symbol? Such
symbols are not used in contexts where an address could alternatively be
expected, so the correct sequence, and in PIC or PIE code indeed the only
valid, for direct references from code is LUI/ADDI. Since you're fiddling
with linker relaxation code here, you may well take the opportunity and
relax it to LUI/ADDI, or ADDI alone if the value is small. There may be
an issue with RV64 objects if the value turns out outside the 32-bit range
though, which will be a relocation overflow.
Maciej
next prev parent reply other threads:[~2023-08-08 9:49 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-27 16:48 Joseph Faulls
2023-07-27 17:02 ` Andreas Schwab
2023-07-27 21:08 ` Palmer Dabbelt
2023-07-28 1:02 ` Nelson Chu
2023-07-28 1:15 ` Nelson Chu
2023-07-28 9:18 ` [EXTERNAL] " Joseph Faulls
2023-07-28 15:03 ` Palmer Dabbelt
2023-07-28 15:52 ` Joseph Faulls
2023-07-28 16:12 ` Palmer Dabbelt
2023-08-08 9:49 ` Maciej W. Rozycki [this message]
2023-08-08 10:38 ` Joseph Faulls
2023-08-08 12:04 ` Maciej W. Rozycki
2023-08-23 11:16 ` Joseph Faulls
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