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Re: [x86-64-psABI] RFC: Add R_X86_64_RELAX_PC32 and R_X86_64_RELAX_PLT32
- From: "Jan Beulich" <JBeulich at suse dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: "GCC Development" <gcc at gcc dot gnu dot org>, "x86-64-abi at googlegroups dot com" <x86-64-abi at googlegroups dot com>, "Michael Matz" <matz at suse dot de>
- Date: Wed, 13 May 2015 07:22:25 +0100
- Subject: Re: [x86-64-psABI] RFC: Add R_X86_64_RELAX_PC32 and R_X86_64_RELAX_PLT32
- Authentication-results: sourceware.org; auth=none
- References: <CAMe9rOp9tv1bnUPJ6s=NR7=5srs48Vqn5-L0Te9agSNSUTyrkw at mail dot gmail dot com> <alpine dot LSU dot 2 dot 20 dot 1505111744400 dot 4883 at wotan dot suse dot de> <CAMe9rOqcLsgDsqFU5mOnA6fQ+wRsNwCpJLiRYDKS1mhcdqfyoA at mail dot gmail dot com> <CAMe9rOokKUoQ=W+oKmFfCHiAeTCAqtYAykOdq2muR+qe-Og6vQ at mail dot gmail dot com>
>>> On 12.05.15 at 20:42, <email@example.com> wrote:
> Here is the updated proposal. I changed nop prefix from 0x48
> to 0x67 and clarified how foo@GOTPCREL(%rip) should be
Mind clarifying how 67 is better than 48?
> I am proposing to add 2 new relocations, R_X86_64_RELAX_PC32 and
> 1. They can only be used on 32-bit direct call/jmp instructions.
> 2. call/jmp instructions must have a 0x67 prefix, which is the address
> size prefix and is ignored by 32-bit direct call/jmp instructions.
The same could have been said several years ago about segment
overrides used with conditional branches, yet they obtained a
meaning (even if only affecting performance, not correctness). Is
it anywhere publicly stated that the address size override will
continue to be ignored?