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

[Farzon Lotfi 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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farzonl wrote:

@boomanaiden154 and @nikic Since you removed and approved the removal of the legacy pass in this commit: https://github.com/llvm/llvm-project/commit/2470857fe701f41278dac33580ca8b0bdb38031f

I wanted to make sure you were ok with our reasons for bringing it back for the DIrectX backend?

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