PGO on Windows-GNU

[leonardo-m]

I am trying to see if -Z pgo-gen is available on Windows-Gnu:

#48346

I am using:

rustc 1.26.0-nightly (188e693b3 2018-03-26)
binary: rustc
commit-hash: 188e693b392116c46f746e86f8521f9621fcfd43
commit-date: 2018-03-26
host: x86_64-pc-windows-gnu
release: 1.26.0-nightly
LLVM version: 6.0

I am using a very small Rust test program:

fn main() {
    println!("Hello");
}

If I compile with:

rustc -Z pgo-gen test.rs

It gives me:

error: debugging option `pgo-gen` requires a string (Z pgo-gen=<value>)

If I compile with (using a random string?):

rustc -Z pgo-gen=abc test.rs

It gives me:

error[E0463]: can't find crate for `profiler_builtins`

[matthiaskrgr]

Hi, I was also struggling with that! :)
The =val is supposed to be the profile file which details are written into after executing the pgo-gen instrumented binary and details are read from when building the binary for the second time with pgo-use.

So
RUSTFLAGS="-Z pgo-gen=profile_data.pgo" cargo build --release
*do things with the program*
RUSTFLAGS="-Z pgo-use=profile_data.pgo" cargo build --release
might work :)

[leonardo-m]

I've tried to do as you say, but perhaps I am doing something wrong. I've created a binary project with cargo (just the hello world), then I've set the variable:

set RUSTFLAGS="-Z pgo-gen=profile_data.pgo"

Then I've compiled:

cargo build --release

It gives me:

error: failed to run `rustc` to learn about target-specific information
Caused by:
  process didn't exit successfully: `rustc - --crate-name ___ --print=file-names "-Z pgo-gen=profile_data.pgo" --target x86_64-pc-windows-gnu --crate-type bin --crate-typ
e rlib` (exit code: 101)
--- stderr
error: multiple input filenames provided

[matthiaskrgr]

Hm, I'm not sure what is going on there now (I also can't reproduce since not a windows user), sorry :/

[leonardo-m]

Using:

rustc 1.35.0-nightly (3de010678 2019-04-11)
binary: rustc
commit-hash: 3de0106789468b211bcc3a25c09c0cf07119186
commit-date: 2019-04-11
host: x86_64-pc-windows-gnu
release: 1.35.0-nightly
LLVM version: 8.0

Calling rustc directly gives:

...>rustc -O -Z pgo-gen=profile_data.pgo test.rs
error[E0463]: can't find crate for `profiler_builtins`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0463`.

[mati865]

GNU toolchain is built without profiler: https://github.com/rust-lang/rust/blob/9a612b2348212d84fa0b839a4c18e4a13fafaf05/appveyor.yml

[michaelwoerister]

I wonder if we could just enable the profiler on *-pc-windows-gnu.

[mati865]

I think I can find time this week to test it.
I'm almost sure PGO was broken on some older GCC version but I cannot recall the details.

[mati865]

Status update:
I've got it working few days ago but pushing this upstream is blocked on upgrading compiler-builtins to 0.1.15. It was meant to be done by #60841 but was backed off.