Stream: git-wasmtime

Topic: wasmtime / issue #9486 Large `.rela` sections for debug info

Wasmtime GitHub notifications bot (Oct 19 2024 at 22:01):

SingleAccretion edited issue #9486:

Reproduction:

> wasmtime compile -D debug-info -O opt-level=0 wasm-with-di.wasm
> llvm-objdump wasm-with-di.cwasm

Expected result: the output does not contain an excessive number of relocations.

Actual result: there are lots of them:

  8 .debug_abbrev      000704e1 0000000000000000 DEBUG
  9 .debug_str         00164a48 0000000000000000 DEBUG
 10 .debug_line        00247334 0000000000000000 DEBUG
 11 .rela.debug_line   00055ef0 0000000000000000
 12 .debug_ranges      0003e530 0000000000000000 DEBUG
 13 .rela.debug_ranges 00097fb0 0000000000000000
 14 .debug_loc         0062e922 0000000000000000 DEBUG
 15 .rela.debug_loc    00cc02a0 0000000000000000
 16 .debug_info        00200ebf 0000000000000000 DEBUG
 17 .rela.debug_info   0065c958 0000000000000000
 18 .debug_frame       0009ada8 0000000000000000 DEBUG
 19 .rela.debug_frame  000abe40 0000000000000000

Looking at .debug_loc in particular, we can see the following for the very first location list:

> llvm-objdump -j .rela.debug_loc -x wasm-with-di.cwasm > rel.txt

RELOCATION RECORDS FOR [.debug_loc]:
OFFSET           TYPE                     VALUE
0000000000000000 R_X86_64_64              wasm[0]::function[41]::_start+0x26
0000000000000008 R_X86_64_64              wasm[0]::function[41]::_start+0x5b
0000000000000013 R_X86_64_64              wasm[0]::function[41]::_start+0x5b
000000000000001b R_X86_64_64              wasm[0]::function[41]::_start+0x68
0000000000000026 R_X86_64_64              wasm[0]::function[41]::_start+0x68
000000000000002e R_X86_64_64              wasm[0]::function[41]::_start+0x91
0000000000000049 R_X86_64_64              wasm[0]::function[41]::_start+0x73
0000000000000051 R_X86_64_64              wasm[0]::function[41]::_start+0x81
000000000000005c R_X86_64_64              wasm[0]::function[41]::_start+0x81
0000000000000064 R_X86_64_64              wasm[0]::function[41]::_start+0x88

The debug info and code are part of the same 'object file' - much of this should be unnecessary.

Wasmtime GitHub notifications bot (Oct 22 2024 at 15:00):

alexcrichton commented on issue #9486:

Oh wow yeah those are huge! Definitely seems reasonable to remove as it's all local within the same binary.

Wasmtime GitHub notifications bot (Oct 24 2024 at 18:37):

alexcrichton added the wasmtime:debugging label to Issue #9486.

Last updated: Nov 22 2024 at 17:03 UTC