[SimplifyCFG] Avoid redundant calls in gather. (NFC) (#154133)

Split out from #154007 as it
showed compile time improvements

NFC as there needs to be at least two icmps that is part of the chain.

Author: andjo403

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

@@ -565,6 +565,9 @@ struct ConstantComparesGatherer {
   /// Number of comparisons matched in the and/or chain
   unsigned UsedICmps = 0;
 
+  /// If the elements in Vals matches the comparisons
+  bool IsEq = false;
+
   /// Construct and compute the result for the comparison instruction Cond
   ConstantComparesGatherer(Instruction *Cond, const DataLayout &DL) : DL(DL) {
     gather(Cond);
@@ -736,23 +739,23 @@ struct ConstantComparesGatherer {
   /// vector.
   /// One "Extra" case is allowed to differ from the other.
   void gather(Value *V) {
-    bool isEQ = match(V, m_LogicalOr(m_Value(), m_Value()));
-
+    Value *Op0, *Op1;
+    if (match(V, m_LogicalOr(m_Value(Op0), m_Value(Op1))))
+      IsEq = true;
+    else if (match(V, m_LogicalAnd(m_Value(Op0), m_Value(Op1))))
+      IsEq = false;
+    else
+      return;
     // Keep a stack (SmallVector for efficiency) for depth-first traversal
-    SmallVector<Value *, 8> DFT;
-    SmallPtrSet<Value *, 8> Visited;
-
-    // Initialize
-    Visited.insert(V);
-    DFT.push_back(V);
+    SmallVector<Value *, 8> DFT{Op0, Op1};
+    SmallPtrSet<Value *, 8> Visited{V, Op0, Op1};
 
     while (!DFT.empty()) {
       V = DFT.pop_back_val();
 
       if (Instruction *I = dyn_cast<Instruction>(V)) {
         // If it is a || (or && depending on isEQ), process the operands.
-        Value *Op0, *Op1;
-        if (isEQ ? match(I, m_LogicalOr(m_Value(Op0), m_Value(Op1)))
+        if (IsEq ? match(I, m_LogicalOr(m_Value(Op0), m_Value(Op1)))
                  : match(I, m_LogicalAnd(m_Value(Op0), m_Value(Op1)))) {
           if (Visited.insert(Op1).second)
             DFT.push_back(Op1);
@@ -763,7 +766,7 @@ struct ConstantComparesGatherer {
         }
 
         // Try to match the current instruction
-        if (matchInstruction(I, isEQ))
+        if (matchInstruction(I, IsEq))
           // Match succeed, continue the loop
           continue;
       }
@@ -5103,6 +5106,7 @@ bool SimplifyCFGOpt::simplifyBranchOnICmpChain(BranchInst *BI,
   Value *CompVal = ConstantCompare.CompValue;
   unsigned UsedICmps = ConstantCompare.UsedICmps;
   Value *ExtraCase = ConstantCompare.Extra;
+  bool TrueWhenEqual = ConstantCompare.IsEq;
 
   // If we didn't have a multiply compared value, fail.
   if (!CompVal)
@@ -5112,8 +5116,6 @@ bool SimplifyCFGOpt::simplifyBranchOnICmpChain(BranchInst *BI,
   if (UsedICmps <= 1)
     return false;
 
-  bool TrueWhenEqual = match(Cond, m_LogicalOr(m_Value(), m_Value()));
-
   // There might be duplicate constants in the list, which the switch
   // instruction can't handle, remove them now.
   array_pod_sort(Values.begin(), Values.end(), constantIntSortPredicate);