[llvm] [LegacyPM][DirectX] Add legacy scalarizer back for use in the DirectX backend (PR #107427)

[Aiden Grossman via llvm-commits]

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@@ -340,8 +341,33 @@ class ScalarizerVisitor : public InstVisitor<ScalarizerVisitor, bool> {
   const unsigned ScalarizeMinBits;
 };
 
+class ScalarizerLegacyPass : public FunctionPass {
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boomanaiden154 wrote:

It seems reasonable enough to me. There are still quite a few (late) middle-end passes that support both the NewPM and the legacyPM due to being needed by backends. The main reason for removal was that no one was using the `ScalarizerLegacyPass` and thus there was no test coverage.

If someone is using it, it's reasonable enough to keep it.

https://github.com/llvm/llvm-project/pull/107427