[VPlan] Add m_Deferred. NFC (llvm#133736)

This copies over the implementation of m_Deferred which allows matching
values that were bound in the pattern, and uses it for the (X && Y) ||
(X && !Y) -> X simplifcation.

Author: lukel97

llvm/lib/Transforms/Vectorize/VPlanPatternMatch.h

@@ -66,6 +66,24 @@ struct specificval_ty {
 
 inline specificval_ty m_Specific(const VPValue *VPV) { return VPV; }
 
+/// Stores a reference to the VPValue *, not the VPValue * itself,
+/// thus can be used in commutative matchers.
+struct deferredval_ty {
+  VPValue *const &Val;
+
+  deferredval_ty(VPValue *const &V) : Val(V) {}
+
+  bool match(VPValue *const V) const { return V == Val; }
+};
+
+/// Like m_Specific(), but works if the specific value to match is determined
+/// as part of the same match() expression. For example:
+/// m_Mul(m_VPValue(X), m_Specific(X)) is incorrect, because m_Specific() will
+/// bind X before the pattern match starts.
+/// m_Mul(m_VPValue(X), m_Deferred(X)) is correct, and will check against
+/// whichever value m_VPValue(X) populated.
+inline deferredval_ty m_Deferred(VPValue *const &V) { return V; }
+
 /// Match a specified integer value or vector of all elements of that
 /// value. \p BitWidth optionally specifies the bitwidth the matched constant
 /// must have. If it is 0, the matched constant can have any bitwidth.

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -1053,11 +1053,10 @@ static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
   // TODO: Split up into simpler, modular combines: (X && Y) || (X && Z) into X
   // && (Y || Z) and (X || !X) into true. This requires queuing newly created
   // recipes to be visited during simplification.
-  VPValue *X, *Y, *X1, *Y1;
+  VPValue *X, *Y;
   if (match(&R,
             m_c_BinaryOr(m_LogicalAnd(m_VPValue(X), m_VPValue(Y)),
-                         m_LogicalAnd(m_VPValue(X1), m_Not(m_VPValue(Y1))))) &&
-      X == X1 && Y == Y1) {
+                         m_LogicalAnd(m_Deferred(X), m_Not(m_Deferred(Y)))))) {
     R.getVPSingleValue()->replaceAllUsesWith(X);
     R.eraseFromParent();
     return;