[PATCH] D85408: Let -basic-block-sections=labels emit basicblock metadata in a new .bb_addr_map section, instead of emitting special unary-encoded symbols.

[Han Shen via Phabricator via llvm-commits]

shenhan added a comment.

In D85408#2253055 <https://reviews.llvm.org/D85408#2253055>, @MaskRay wrote:

> I am still reading the patch, but I have noticed one thing worth discussing. `.bb_addr_map` is a non-SHF_ALLOC section (meaning that it is not part of the memory image). An absolute relocation type (`.quad	.Lfunc_begin0`) works but the value is a link-time address, not taking account of the load base (PIE/shared object)). (If .bb_addr_map has the SHF_ALLOC flag, linkers will report a text relocation) How do you intend to use `.bb_addr_map` at runtime?

Regarding "not taking account of the load base (PIE/shared object)" - the profile conversion tool uses addresses in .bb_addr_map section and MMAP entries in perf.data file to construct runtime addresses, so these runtime addresses can be matched with the profile addresses recorded in perf.data file.


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  https://reviews.llvm.org/D85408/new/

https://reviews.llvm.org/D85408