Commits on Oct 6, 2024

1. [RFC][Transforms][IPO] Add func suffix in ArgumentPromotion and DeadA… …

   …rgumentElimination
   
   ArgumentPromotion and DeadArgumentElimination passes could change
   function signatures but the function name remains the same as before
   the transformation. This makes it hard for tracing with bpf programs
   where user tends to use function signature in the source.
   See discussion [1] for details.
   
   This patch added suffix to functions whose signatures
   are changed. The suffix lets users know that function
   signature has changed and they need to impact the IR or binary
   to find modified signature before tracing those functions.
   
   The suffix for ArgumentPromotion is ".argprom" and
   the suffix for DeadArgumentElimination is ".argelim".
   The suffix also gives user hints about what kind of
   transformation has been done.
   
   With this patch, I built a recent linux kernel with
   full LTO enabled. I got 4 functions with only argpromotion like
     set_track_update.argelim.argprom
     pmd_trans_huge_lock.argprom
     ...
   I got 1058 functions with only deadargelim like
     process_bit0.argelim
     pci_io_ecs_init.argelim
     ...
   I got 3 functions with both argpromotion and deadargelim
     set_track_update.argelim.argprom
     zero_pud_populate.argelim.argprom
     zero_pmd_populate.argelim.argprom
   
   There are some concerns about func suffix may impact sample based
   profiling. I did some experiments and show that this is not the
   case. The sample profiling gets func name from dwarf and those
   func names in dwarf does not have suffixes added by this patch
   and sample profiling works fine with this patch.
   
     [1] llvm#104678

   Yonghong Song committed Oct 6, 2024
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