From: Xi Ruoyao <xry111@xry111.site>
To: mengqinggang <mengqinggang@loongson.cn>, binutils@sourceware.org
Cc: xuchenghua@loongson.cn, liuzhensong@loongson.cn,
chenglulu@loongson.cn, i.swmail@xen0n.name, maskray@google.com
Subject: Re: [PATCH v1 0/6] LoongArch linker relaxation support.
Date: Mon, 05 Dec 2022 16:43:45 +0800 [thread overview]
Message-ID: <31f6c836d79a8569d95a36c6b6fcfafddbdf459e.camel@xry111.site> (raw)
In-Reply-To: <20221205080453.1352069-1-mengqinggang@loongson.cn>
On Mon, 2022-12-05 at 16:04 +0800, mengqinggang wrote:
> Now, only the instrunctions expand from macro (la.local, la.got, etc.) at
> assembly time can be relaxed, because gcc instruction scheduling causes relax
> unable to handle some special cases. Gcc can add -mno-explicit-relocs option
> to generate macro instrunction.
Frankly, I don't like this. Can the compiler explicitly emit some
relocations to mark a instruction chain suitable for relaxation? Some
random thought:
.reloc R_LARCH_RELOC_X 1
pcalau12i $a0, %got_pc_hi20(sym_a)
.reloc R_LARCH_RELOC_X 2
pcalau12i $a1, %got_pc_hi20(sym_b)
.reloc R_LARCH_RELOC_X 1
ld.d $a0, $a0, %got_pc_lo12(sym_a)
.reloc R_LARCH_RELOC_X 2
ld.d $a1, $a1, %got_pc_lo12(sym_b)
.reloc R_LARCH_RELOC_X 1
ld.d $a0, $a0, 0
.reloc R_LARCH_RELOC_X 2
ld.d $a1, $a1, 0
Here "R_LARCH_RELOC_X" is an imaginary relocation type. We may be able
to use the different values of the 32-bit addend to distinguish two load
sequences interleaved after scheduling (I don't think there will be more
than 2147483647 load sequences in an object file).
This is just some random thoughts, I don't understand the linking
process very well anyway.
--
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University
next prev parent reply other threads:[~2022-12-05 8:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-05 8:04 mengqinggang
2022-12-05 8:04 ` [PATCH v1 1/6] LoongArch: include: Add support for linker relaxation mengqinggang
2022-12-05 8:24 ` Xi Ruoyao
2022-12-06 2:59 ` mengqinggang
2022-12-05 8:04 ` [PATCH v1 2/6] LoongArch: bfd: " mengqinggang
2022-12-05 8:04 ` [PATCH v1 3/6] LoongArch: opcodes: " mengqinggang
2022-12-05 9:43 ` Andreas Schwab
2022-12-05 8:04 ` [PATCH v1 4/6] LoongArch: binutils: " mengqinggang
2022-12-05 8:04 ` [PATCH v1 5/6] LoongArch: gas: " mengqinggang
2022-12-05 9:47 ` Andreas Schwab
2022-12-05 8:04 ` [PATCH v1 6/6] LoongArch: ld: " mengqinggang
2022-12-05 8:31 ` Xi Ruoyao
2022-12-05 8:43 ` Xi Ruoyao [this message]
2022-12-06 1:58 ` [PATCH v1 0/6] LoongArch linker relaxation support mengqinggang
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