Compile backtrace-related deps with opt-level=s

[erikdesjardins]

Locally, this shrinks a stripped helloworld by 8k (~2%), which isn't huge but it's something.

I also tried opt-level=z but it produces the same result. opt-level=s is preferrable in that case since it inhibits fewer optimizations.

[rustbot]

r? @Mark-Simulacrum

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[erikdesjardins]

After this, the largest functions in helloworld-tiny are

┌─────────────────────────────────────────────────────────────────────────────────────────────────┬────────────┐
│ Symbol                                                                                          │       Size │
├─────────────────────────────────────────────────────────────────────────────────────────────────┼────────────┤
│ std::sys_common::backtrace::_print_fmt::{{closure}}                                             │  15.88 KiB │
│ std::backtrace_rs::symbolize::gimli::Context::new                                               │  14.28 KiB │
│ addr2line::ResUnit<R>::find_function_or_location::{{closure}}                                   │   9.41 KiB │
│ addr2line::Lines::parse                                                                         │   7.78 KiB │
│ miniz_oxide::inflate::core::decompress                                                          │   6.81 KiB │
│ std::backtrace_rs::symbolize::gimli::libs_dl_iterate_phdr::callback                             │   4.86 KiB │
│ gimli::read::unit::parse_attribute                                                              │   4.12 KiB │
│ miniz_oxide::inflate::core::REVERSED_BITS_LOOKUP                                                │      4 KiB │
│ main                                                                                            │   3.42 KiB │
│ addr2line::function::Function<R>::parse_children                                                │   3.27 KiB │
│ std::backtrace_rs::symbolize::SymbolName::new                                                   │   3.24 KiB │
│ gimli::read::line::DebugLine<R>::program                                                        │   3.23 KiB │
│ core::slice::sort::recurse                                                                      │   3.19 KiB │
│ <&T as core::fmt::Display>::fmt                                                                 │   3.16 KiB │
│ alloc::raw_vec::RawVec<T,A>::reserve_for_push                                                   │   2.81 KiB │
│ gimli::read::abbrev::AbbreviationsCache::get                                                    │   2.30 KiB │
│ gimli::read::line::parse_attribute                                                              │   2.27 KiB │
│ gimli::read::dwarf::Unit<R>::new                                                                │   2.27 KiB │
│ <&str as core::str::pattern::Pattern>::is_contained_in                                          │   2.11 KiB │
│ std::backtrace_rs::symbolize::gimli::elf::<impl std::backtrace_rs::symbolize::gimli::Mapping>::new_debug
                                                                                                  │   1.94 KiB │
│ rustc_demangle::v0::Printer::print_const                                                        │   1.89 KiB │
│ std::backtrace_rs::print::BacktraceFrameFmt::print_raw_with_column                              │   1.75 KiB │
...

[Kobzol]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 03e7e9e with merge 2105cee...

[bors]

☀️ Try build successful - checks-actions
Build commit: 2105cee (2105ceeb0f23267f160392bd0e43b1c647590aac)

[rust-timer]

Finished benchmarking commit (2105cee): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.1%	[0.2%, 1.9%]	7
Regressions ❌ (secondary)	1.0%	[0.2%, 3.7%]	29
Improvements ✅ (primary)	-1.4%	[-4.2%, -0.2%]	20
Improvements ✅ (secondary)	-1.2%	[-3.6%, -0.6%]	10
All ❌✅ (primary)	-0.7%	[-4.2%, 1.9%]	27

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	2.7%	[1.4%, 4.0%]	2
Regressions ❌ (secondary)	2.6%	[1.9%, 4.5%]	7
Improvements ✅ (primary)	-7.4%	[-14.2%, -1.8%]	5
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-4.5%	[-14.2%, 4.0%]	7

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	2.1%	[2.0%, 2.1%]	2
Regressions ❌ (secondary)	2.1%	[1.8%, 3.1%]	7
Improvements ✅ (primary)	-3.0%	[-6.1%, -1.0%]	10
Improvements ✅ (secondary)	-2.2%	[-3.2%, -1.1%]	2
All ❌✅ (primary)	-2.2%	[-6.1%, 2.1%]	12

Binary size

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.0%, 0.5%]	10
Regressions ❌ (secondary)	0.6%	[0.6%, 0.6%]	3
Improvements ✅ (primary)	-1.7%	[-9.6%, -0.0%]	63
Improvements ✅ (secondary)	-1.9%	[-3.7%, -0.1%]	80
All ❌✅ (primary)	-1.4%	[-9.6%, 0.5%]	73

Bootstrap: 670.21s -> 668.391s (-0.27%)
Artifact size: 310.75 MiB -> 310.70 MiB (-0.02%)

[erikdesjardins]

Didn't expect the perf regressions to be so large, will investigate.

@rustbot author

[erikdesjardins]

Perf regressions for helloworld (./target/release/collector profile_local cachegrind +6f3eb1ce3d50246b2cbc5de3107c0f34889f5cc6 --rustc2 +2105ceeb0f23267f160392bd0e43b1c647590aac --include helloworld --profiles Opt --scenarios IncrUnchanged) seem to be mostly in the dynamic linker which is odd, since we don't dynamically link these backtrace crates. So I'm not sure why this would make the compiler itself slower to dynamically link.

--------------------------------------------------------------------------------
-- Function:file summary
--------------------------------------------------------------------------------
  Ir_____  function:file

> 458,404  _dl_lookup_symbol_x:
  411,604    ./elf/../sysdeps/generic/dl-new-hash.h
   46,800    ./elf/./elf/dl-lookup.c

> 203,746  <rustc_middle::ty::Ty as rustc_serialize::serialize::Decodable<rustc_metadata::rmeta::decoder::DecodeContext>>::decode:???

> 136,876  do_lookup_x:
  132,196    ./elf/./elf/dl-lookup.c
    2,600    ./elf/../sysdeps/generic/ldsodefs.h
    2,080    ./elf/../sysdeps/generic/dl-protected.h

> 103,302  _dl_addr:./elf/./elf/dl-addr.c

>  83,216  <rustc_middle::ty::context::CtxtInterners>::intern_ty:???

>  56,186  _dl_relocate_object:
   24,976    ./elf/./elf/dl-reloc.c
   15,630    ./elf/../sysdeps/x86_64/dl-machine.h
   14,011    ./elf/./elf/do-rel.h
    1,569    ./elf/../sysdeps/generic/ldsodefs.h

...

[bors]

☔ The latest upstream changes (presumably #123608) made this pull request unmergeable. Please resolve the merge conflicts.

[Mark-Simulacrum]

I think we are dynamically linking these crates? rustc uses a shared library for std today.

In any case I think this likely can't proceed given the regressions so I'm going to go ahead and close (but feel free to reopen if you want to invest in alternative designs etc).