Re: RFC: Add -mshared option to x86 ELF assembler
From: H. Peter Anvin
Date: Wed May 20 2015 - 16:32:28 EST
On 05/20/2015 01:02 PM, Andy Lutomirski wrote:
>>
>> I got
>>
>> [hjl@gnu-tools-1 kernel.org]$ readelf -r old/vmlinux.o | head -5
>>
>> Relocation section '.rela.text' at offset 0xafea2f0 contains 205717 entries:
>> Offset Info Type Sym. Value Sym. Name + Addend
>> 000000000001 1253100000002 R_X86_64_PC32 0000000000001e70 __fentry__ - 4
>> 000000000009 1c8c00000002 R_X86_64_PC32 0000000000000000 .data + 51bc
>> [hjl@gnu-tools-1 kernel.org]$ readelf -r new/vmlinux.o | head -5
>>
>> Relocation section '.rela.text' at offset 0xafea280 contains 205711 entries:
>> Offset Info Type Sym. Value Sym. Name + Addend
>> 000000000001 1253100000002 R_X86_64_PC32 0000000000001e70 __fentry__ - 4
>> 000000000009 1c8c00000002 R_X86_64_PC32 0000000000000000 .data + 51bc
>> [hjl@gnu-tools-1 kernel.org]$
>>
>> It removes 6 relocations. On gcc master branch,
>>
>> [hjl@gnu-tools-1 gcc-misc]$ size build-x86_64-linux*/gcc/cc1
>> text data bss dec hex filename
>> 21529621 62256 1348312 22940189 15e0a1d build-x86_64-linux.branch/gcc/cc1
>> 21529749 62256 1348312 22940317 15e0a9d build-x86_64-linux/gcc/cc1
>> [hjl@gnu-tools-1 gcc-misc]$ size build-x86_64-linux*/gcc/cc1plus
>> text data bss dec hex filename
>> 23713509 62400 1372760 25148669 17fbcfd build-x86_64-linux.branch/gcc/cc1plus
>> 23713669 62400 1372760 25148829 17fbd9d build-x86_64-linux/gcc/cc1plus
>> [hjl@gnu-tools-1 gcc-misc]$
>>
>> It is more effective. I will run more tests.
>
> This seems like a sensible idea, but I can imagine it breaking some
> weird use cases (like that one Linux thing). Is that okay?
>
What about the patch I posted recently?
-hpa
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