Support of link time symbols reorder to improve performance

[Xi Ruoyao]

On Fri, 2021-05-07 at 00:06 +0800, 陈云星 via Gcc-help wrote:
> From llvm community: 
> https://reviews.llvm.org/rG1a33c0f2422c97dbfdbf11e561bb7823d71e3145 <
> https://reviews.llvm.org/rG1a33c0f2422c97dbfdbf11e561bb7823d71e3145>
> 
> LLD linker has an option :  --symbol-ordering-file
> 
> Which support direct linker to sort symbol in result object by a user
> supplied file;
> 
> This improve performance by reduce instruction cache miss.
> 
> The hottest function will cluster and code cache hit rate will be high.
> 
> Does gnu linker can support this ?

I think with -ffunction-sections and -fdata-sections, and a ld script it
can be achieved.  But it may be very painful.

Cc binutils, as it's a more proper location to discuss this.
-- 
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University