[InstCombine] Cleanup code in foldSelectICmpAndOr; NFC

[goldstein.w.n]

Summary

There was just alot of boolean logic to propegate conditions that seem
clearer in conditions.

[nikic]

LGTM

[goldstein.w.n]

Rebase

[goldstein.w.n]

Rebase

[goldstein.w.n]

Rebase

[goldstein.w.n]

Rebase

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

if (IC->isEquality()) {
 
     const APInt *C1;
     if (!match(CmpLHS, m_And(m_Value(), m_Power2(C1))))
       return nullptr;
 
     V = CmpLHS;
     C1Log = C1->logBase2();
     IsEqualZero = IC->getPredicate() == ICmpInst::ICMP_EQ;
-  } else if (IC->getPredicate() == ICmpInst::ICMP_SLT ||
-             IC->getPredicate() == ICmpInst::ICMP_SGT) {
+  } else {
     // We also need to recognize (icmp slt (trunc (X)), 0) and
     // (icmp sgt (trunc (X)), -1).
-    IsEqualZero = IC->getPredicate() == ICmpInst::ICMP_SGT;
-    if ((IsEqualZero && !match(CmpRHS, m_AllOnes())) ||
-        (!IsEqualZero && !match(CmpRHS, m_Zero())))
+    if (IC->getPredicate() == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes()))
+      IsEqualZero = true;
+    if (IC->getPredicate() == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero()))
+      IsEqualZero = false;
+    else
       return nullptr;
 
     if (!match(CmpLHS, m_OneUse(m_Trunc(m_Value(V)))))
       return nullptr;
 
     C1Log = CmpLHS->getType()->getScalarSizeInBits() - 1;
     NeedAnd = true;
-  } else {
-    return nullptr;
   }
 
+  Value *Or, *Y;
   const APInt *C2;
-  bool OrOnTrueVal = false;
-  bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2)));
-  if (!OrOnFalseVal)
-    OrOnTrueVal = match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2)));
-
-  if (!OrOnFalseVal && !OrOnTrueVal)
+  bool NeedXor;
+  if (match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2)))) {
+    Y = TrueVal;
+    Or = FalseVal;
+    NeedXor = !IsEqualZero;
+  } else if (match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2)))) {
+    Y = FalseVal;
+    Or = TrueVal;
+    NeedXor = IsEqualZero;
+  } else {
     return nullptr;
-
-  Value *Y = OrOnFalseVal ? TrueVal : FalseVal;
+  }
 
   unsigned C2Log = C2->logBase2();
 
-  bool NeedXor = (!IsEqualZero && OrOnFalseVal) || (IsEqualZero && OrOnTrueVal);
   bool NeedShift = C1Log != C2Log;
   bool NeedZExtTrunc = Y->getType()->getScalarSizeInBits() !=
                        V->getType()->getScalarSizeInBits();
 
   // Make sure we don't create more instructions than we save.
-  Value *Or = OrOnFalseVal ? FalseVal : TrueVal;
   if ((NeedShift + NeedXor + NeedZExtTrunc) >
       (IC->hasOneUse() + Or->hasOneUse()))
     return nullptr;
 
   if (NeedAnd) {
     // Insert the AND instruction on the input to the truncate.
     APInt C1 = APInt::getOneBitSet(V->getType()->getScalarSizeInBits(), C1Log);
     V = Builder.CreateAnd(V, ConstantInt::get(V->getType(), C1));