[llvm] [VPlan] Add simple driver option to run some individual transforms. (PR #178522)

[Andrei Elovikov via llvm-commits]

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@@ -0,0 +1,38 @@
+; REQUIRES: asserts
+
+; Test the licm VPlan transform that performs loop-invariant code motion.
+
+; RUN: opt -passes=loop-vectorize -vplan-test-transform='widen-from-metadata,licm,print' -disable-output %s 2>&1 | FileCheck %s
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eas wrote:

Alternatively, make that a separate LLVM pass and run like 
```
opt -disable-output -p vplan-test<widen-from-metadata;licm> < %s | FileCheck %s
```
The "print" could be implicit for this new `vplan-test` pass and it could also use stdout instead of stderr so that  we wouldn't need to write "2>&1" (and the errors wouldn't be eaten by FileCheck if they happen).

https://github.com/llvm/llvm-project/pull/178522