[PATCH] D142556: [DebugInfo] Merge partially matching chains of inlined locations

Fri Feb 10 16:46:26 PST 2023

dstenb added a comment.

In D142556#4119696 <https://reviews.llvm.org/D142556#4119696>, @dblaikie wrote:

> I'm a bit confused by all these reports - at least with my `bloaty` locally, "+100%" would mean the section doubled in size (100% growth) but it shows "+100%" even for a section that shrunk (.debug_line_str) slightly... Confusing.
>
> but the overall numbers still sound OK.

Yes, I thought that the output format looked odd. That was with `bloaty` built from main (52948c), which we can compare to v1.1 (for a small example binary):

  $ diff -u <(./bloaty-1.1 with.out -- without.out) <(./bloaty-52948c1 with.out -- without.out)
  --- /dev/fd/63	2023-02-11 01:25:09.785684383 +0100
  +++ /dev/fd/62	2023-02-11 01:25:09.785684383 +0100
  @@ -1,8 +1,8 @@
       FILE SIZE        VM SIZE    
    --------------  -------------- 
  -   +11%     +26  [ = ]       0    .debug_info
  -  +6.5%     +15  [ = ]       0    .debug_abbrev
  -  +6.7%      +8  [ = ]       0    .debug_addr
  -  +0.1%      +6  [ = ]       0    [Unmapped]
  -  +0.5%      +1  [ = ]       0    .debug_line
  -  +0.3%     +56  [ = ]       0    TOTAL
  +  +115%     +26  [ = ]       0    .debug_info
  +  +109%     +15  [ = ]       0    .debug_abbrev
  +  +114%      +8  [ = ]       0    .debug_addr
  +  +111%      +6  [ = ]       0    .debug_str_offsets
  +  +101%      +1  [ = ]       0    .debug_line
  +  +100% +17.1Ki  +100% +2.61Ki    TOTAL

Although they find the same number of bytes, v1.1 reports an +11% increase for .debug_info for this example compared to +115% when using bloaty from main. Perhaps it is broken on main?

I don't have access to run v1.1 on the binaries in question now, but if we look at the ratios for the `"#bytes"` diff lines from llvm-dwarfdump in one of my earlier comments we can see that the ratios are smaller than how I interpreted bloaty's output, similar to this small example.

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https://reviews.llvm.org/D142556