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71 lines
2.3 KiB
Markdown
71 lines
2.3 KiB
Markdown
This folder contains tests for MIR optimizations.
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The `mir-opt` test format emits MIR to extra files that you can automatically update by specifying
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`--bless` on the command line (just like `ui` tests updating `.stderr` files).
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# `--bless`able test format
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By default 32 bit and 64 bit targets use the same dump files, which can be problematic in the
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presence of pointers in constants or other bit width dependent things. In that case you can add
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```
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// EMIT_MIR_FOR_EACH_BIT_WIDTH
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```
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to your test, causing separate files to be generated for 32bit and 64bit systems.
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## Testing a particular MIR pass
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If you are only testing the behavior of a particular mir-opt pass on some specific input (as is
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usually the case), you should add
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```
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//@ test-mir-pass: PassName
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```
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to the top of the file. This makes sure that other passes don't run which means you'll get the input
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you expected and your test won't break when other code changes. This also lets you test passes
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that are disabled by default.
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## Emit a diff of the mir for a specific optimization
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This is what you want most often when you want to see how an optimization changes the MIR.
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```
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// EMIT_MIR $file_name_of_some_mir_dump.diff
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```
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## Emit mir after a specific optimization
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Use this if you are just interested in the final state after an optimization.
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```
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// EMIT_MIR $file_name_of_some_mir_dump.after.mir
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```
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## Emit mir before a specific optimization
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This exists mainly for completeness and is rarely useful.
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```
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// EMIT_MIR $file_name_of_some_mir_dump.before.mir
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```
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# FileCheck directives
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The LLVM FileCheck tool is used to verify the contents of output MIR against `CHECK` directives
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present in the test file. This works on the runtime MIR, generated by `--emit=mir`, and not
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on the output of a individual passes.
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Use `// skip-filecheck` to prevent FileCheck from running.
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To check MIR for function `foo`, start with a `// CHECK-LABEL fn foo(` directive.
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`{{regex}}` syntax allows to match `regex`.
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`[[name:regex]]` syntax allows to bind `name` to a string matching `regex`, and refer to it
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as `[[name]]` in later directives, `regex` should be written not to match a leading space.
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Use `[[my_local:_.*]]` to name a local, and `[[my_bb:bb.*]]` to name a block.
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Documentation for FileCheck is available here: https://www.llvm.org/docs/CommandGuide/FileCheck.html
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