<div dir="ltr"><div dir="ltr">On Sat, Sep 24, 2022 at 6:53 AM chen <<a href="mailto:chenm003@163.com">chenm003@163.com</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="line-height:1.7;color:rgb(0,0,0);font-size:14px;font-family:Arial"><div style="margin:0px">Hi Song,</div><div style="margin:0px"><br></div><div style="margin:0px">Sorry for delay.</div><div style="margin:0px">The new patches just clean up some code that assume already declare defined(PIC) on aarch64, so I still think we need not do like this, declare -DPIC on cmdline is more general.</div><div style="margin:0px"><font face="arial"><span style="white-space:pre-wrap">On previous error message of sad-a.S, the compile option is '-fPIC', I guess we need '-fPIC -DPIC'</span></font></div><div style="margin:0px"><span style="font-family:arial;white-space:pre-wrap"><br></span></div><div style="margin:0px"><span style="font-family:arial;white-space:pre-wrap">Regards,
</span><span style="font-family:arial;white-space:pre-wrap">Min Chen</span></div></div></blockquote><div><br></div><div>Hi Min, sorry but I just saw your question. I do not understand the request.</div><div>adrp+add is just strictly superior to ldr (which uses a constant pool and does not decrease code size) and avoids text relocations (which are prohibited in many systems). `ldr \rd, =\val+\offset` should just be removed. adrp+add also works on Mach-O systems as well.</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="line-height:1.7;color:rgb(0,0,0);font-size:14px;font-family:Arial"><pre><div>At 2022-09-24 15:21:35, "Fangrui Song" <<a href="mailto:maskray@google.com" target="_blank">maskray@google.com</a>> wrote:</div>>Ping. The breaks lld build and some binutils configurating defaulting
>to disallow text relocations.
>
>On 2022-08-29, Fangrui Song wrote:
>>On 2022-08-29, Fangrui Song wrote:
>>>On 2022-08-30, chen wrote:
>>>>Hi Song,
>>>>
>>>>
>>>>Thank you for your patch.
>>>>
>>>>
>>>>However, syntax of ':lo12:' depends on compiler, so more general LDR is better in here.
>>>>
>>>>
>>>>Regards,
>>>>Min Chen
>>>
>>>:lo12: is standard aarch64 assembly syntax.
>>>Which aarch64 compiler supported by x265 does not support :lo12:?
>>
>>Note that LDR has another problem that it produced an absolute relocation R_AARCH64_ABS64. It will trigger an error
>>when text relocations are disabled (default in ld.lld. See <a href="https://maskray.me/blog/2020-12-19-lld-and-gnu-linker-incompatibilities#:~:text=Text%20relocations" target="_blank">https://maskray.me/blog/2020-12-19-lld-and-gnu-linker-incompatibilities#:~:text=Text%20relocations</a>)
>>
>>```
>>% : && /usr/bin/c++ -fPIC -O3 -DNDEBUG -Wl,-Bsymbolic,-znoexecstack -shared ...
>>ld: error: relocation R_AARCH64_ABS64 cannot be used against local
>>symbol; recompile with -fPIC
>>>>>defined in sad-a.S.o
>>>>>>>> referenced by sad-a.S.o:(.text+0x9B00)
>>```
>>
>>adrp+add work fine.
>>
>>(I am a maintainer of lld/ELF.)
>>
>>>>At 2022-08-30 02:33:37, "Fangrui Song" <<a href="mailto:maskray@google.com" target="_blank">maskray@google.com</a>> wrote:
>>>>>The ldr pseudo-instruction uses a literal pool, which is less efficient
>>>>>and does not decrease the code size.
>>>>>---
>>>>>source/common/aarch64/asm.S | 4 +---
>>>>>1 file changed, 1 insertion(+), 3 deletions(-)
>>>>>
>>>>>diff --git a/source/common/aarch64/asm.S b/source/common/aarch64/asm.S
>>>>>index 399c37cf2..2506f50aa 100644
>>>>>--- a/source/common/aarch64/asm.S
>>>>>+++ b/source/common/aarch64/asm.S
>>>>>@@ -130,11 +130,9 @@ ELF .size \name, . - \name
>>>>> adrp \rd, \val+(\offset)
>>>>> add \rd, \rd, :lo12:\val+(\offset)
>>>>> .endif
>>>>>-#elif defined(PIC)
>>>>>+#else
>>>>> adrp \rd, \val+(\offset)
>>>>> add \rd, \rd, :lo12:\val+(\offset)
>>>>>-#else
>>>>>- ldr \rd, =\val+\offset
>>>>>#endif
>>>>>.endm
>>>>>
>>>>>--
>>>>>2.37.2.672.g94769d06f0-goog
>>>>>
>>>>>_______________________________________________
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>>>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr">宋方睿</div></div></div>