a3eb2f0f22
Use span of placeholders in format_args!() expansion.
`format_args!("{}", x)` expands to something that contains `Argument::new_display(&x)`. That entire expression was generated with the span of `x`.
After this PR, `&x` uses the span of `x`, but the `new_display` call uses the span of the `{}` placeholder within the format string. If an implicitly captured argument was used like in `format_args!("{x}")`, both use the span of the `{x}` placeholder.
This fixes https://github.com/rust-lang/rust/issues/109576, and also allows for more improvements to similar diagnostics in the future, since the usage of `x` can now be traced to the exact `{}` placeholder that required it to be `Display` (or `Debug` etc.)
This folder contains tests for MIR optimizations.
The mir-opt test format emits MIR to extra files that you can automatically update by specifying
--bless on the command line (just like ui tests updating .stderr files).
--blessable test format
By default 32 bit and 64 bit targets use the same dump files, which can be problematic in the presence of pointers in constants or other bit width dependent things. In that case you can add
// EMIT_MIR_FOR_EACH_BIT_WIDTH
to your test, causing separate files to be generated for 32bit and 64bit systems.
Unit testing
If you are only testing the behavior of a particular mir-opt pass on some specific input (as is usually the case), you should add
// unit-test: PassName
to the top of the file. This makes sure that other passes don't run which means you'll get the input you expected and your test won't break when other code changes.
Emit a diff of the mir for a specific optimization
This is what you want most often when you want to see how an optimization changes the MIR.
// EMIT_MIR $file_name_of_some_mir_dump.diff
Emit mir after a specific optimization
Use this if you are just interested in the final state after an optimization.
// EMIT_MIR $file_name_of_some_mir_dump.after.mir
Emit mir before a specific optimization
This exists mainly for completeness and is rarely useful.
// EMIT_MIR $file_name_of_some_mir_dump.before.mir