[llvm] Add flags to dump IR to a file before and after LLVM passes (PR #65179)

[Nuri Amari via llvm-commits]

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@@ -0,0 +1,71 @@
+; RUN: mkdir -p %t/logs
+; RUN: rm -rf %t/logs
+
+; Basic dump before and after a single module pass
+; RUN: opt %s -disable-output -passes='no-op-module' -ir-dump-directory %t/logs -dump-after=no-op-module -dump-before=no-op-module
+; RUN: find %t/logs -type f -print | FileCheck %s --check-prefix=SINGLE-RUN -DSOURCE_FILE_NAME=%s
+; SINGLE-RUN-DAG: [[SOURCE_FILE_NAME]]/0.NoOpModulePass.0-before.ll
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NuriAmari wrote:

The first `0` means this is the first pass to run at this nesting level. The second `0` means this is the first `NoOpModulePass` to run at this nesting level.

While dumping to files is less noisy, without this first number you lose the sequence in which passes run, which makes it harder to trace issues.

https://github.com/llvm/llvm-project/pull/65179