[NFC][InstCombine] Extract freelyInvertAllUsersOf() out of canonicalizeICmpPredicate()

I'd like to use it in an upcoming fold.

Author: LebedevRI

llvm/include/llvm/Transforms/InstCombine/InstCombiner.h

@@ -263,8 +263,7 @@ class LLVM_LIBRARY_VISIBILITY InstCombiner {
   }
 
   /// Given i1 V, can every user of V be freely adapted if V is changed to !V ?
-  /// InstCombine's canonicalizeICmpPredicate() must be kept in sync with this
-  /// fn.
+  /// InstCombine's freelyInvertAllUsersOf() must be kept in sync with this fn.
   ///
   /// See also: isFreeToInvert()
   static bool canFreelyInvertAllUsersOf(Value *V, Value *IgnoredUser) {

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -5328,26 +5328,8 @@ CmpInst *InstCombinerImpl::canonicalizeICmpPredicate(CmpInst &I) {
   I.setPredicate(CmpInst::getInversePredicate(Pred));
   I.setName(I.getName() + ".not");
 
-  // And now let's adjust every user.
-  for (User *U : I.users()) {
-    switch (cast<Instruction>(U)->getOpcode()) {
-    case Instruction::Select: {
-      auto *SI = cast<SelectInst>(U);
-      SI->swapValues();
-      SI->swapProfMetadata();
-      break;
-    }
-    case Instruction::Br:
-      cast<BranchInst>(U)->swapSuccessors(); // swaps prof metadata too
-      break;
-    case Instruction::Xor:
-      replaceInstUsesWith(cast<Instruction>(*U), &I);
-      break;
-    default:
-      llvm_unreachable("Got unexpected user - out of sync with "
-                       "canFreelyInvertAllUsersOf() ?");
-    }
-  }
+  // And, adapt users.
+  freelyInvertAllUsersOf(&I);
 
   return &I;
 }

llvm/lib/Transforms/InstCombine/InstCombineInternal.h

@@ -323,6 +323,8 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
   Instruction *optimizeBitCastFromPhi(CastInst &CI, PHINode *PN);
   Instruction *matchSAddSubSat(SelectInst &MinMax1);
 
+  void freelyInvertAllUsersOf(Value *V);
+
   /// Determine if a pair of casts can be replaced by a single cast.
   ///
   /// \param CI1 The first of a pair of casts.

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -870,6 +870,30 @@ Value *InstCombinerImpl::SimplifySelectsFeedingBinaryOp(BinaryOperator &I,
   return SI;
 }
 
+/// Freely adapt every user of V as-if V was changed to !V.
+/// WARNING: only if canFreelyInvertAllUsersOf() said this can be done.
+void InstCombinerImpl::freelyInvertAllUsersOf(Value *I) {
+  for (User *U : I->users()) {
+    switch (cast<Instruction>(U)->getOpcode()) {
+    case Instruction::Select: {
+      auto *SI = cast<SelectInst>(U);
+      SI->swapValues();
+      SI->swapProfMetadata();
+      break;
+    }
+    case Instruction::Br:
+      cast<BranchInst>(U)->swapSuccessors(); // swaps prof metadata too
+      break;
+    case Instruction::Xor:
+      replaceInstUsesWith(cast<Instruction>(*U), I);
+      break;
+    default:
+      llvm_unreachable("Got unexpected user - out of sync with "
+                       "canFreelyInvertAllUsersOf() ?");
+    }
+  }
+}
+
 /// Given a 'sub' instruction, return the RHS of the instruction if the LHS is a
 /// constant zero (which is the 'negate' form).
 Value *InstCombinerImpl::dyn_castNegVal(Value *V) const {