[llvm] [SelectOpt] Add handling for Select-like operations. (PR #77284)

[Florian Hahn via llvm-commits]

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@@ -129,6 +124,146 @@ class SelectOptimizeImpl {
     Scaled64 NonPredCost;
   };
 
+  /// SelectLike is an abstraction over SelectInst and other operations that can
+  /// act like selects. For example Or(Zext(icmp), X) can be treated like
+  /// select(icmp, X|1, X).
+  class SelectLike {
+  private:
+    SelectLike(Instruction *I) : I(I) {}
+
+    Instruction *I;
+
+  public:
+    /// Match a select or select-like instruction, returning a SelectLike.
+    static SelectLike match(Instruction *I) {
+      // Select instruction are what we are usually looking for.
+      if (isa<SelectInst>(I))
+        return SelectLike(I);
+
+      // An Or(zext(i1 X), Y) can also be treated like a select, with condition
+      // C and values Y|1 and Y.
+      Value *X;
+      if (PatternMatch::match(
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fhahn wrote:

is `PatternMatch::` needed with `using namespace llvm::PatternMatch;` above?

https://github.com/llvm/llvm-project/pull/77284