[ARM] Factorize the calculation of WhichResult in isV*Mask. NFC.

[fhahn]

LGTM, I think it's a nice simplification and was already discussed in D36899. Please check the formatting before committing.

lib/Target/ARM/ARMISelLowering.cpp

5803

Line too long?

[mstorsjo]

lib/Target/ARM/ARMISelLowering.cpp

5803

Indeed, fixed with clang-format-diff locally - will push with that fixed.

lib/Target/ARM/ARMISelLowering.cpp

 
 static bool isVTBLMask(ArrayRef<int> M, EVT VT) {
   // We can handle <8 x i8> vector shuffles. If the index in the mask is out of
   // range, then 0 is placed into the resulting vector. So pretty much any mask
   // of 8 elements can work here.
   return VT == MVT::v8i8 && M.size() == 8;
 }
 
+static unsigned SelectPairHalf(unsigned Elements, ArrayRef<int> Mask, unsigned Index) {
+  if (Mask.size() == Elements * 2)
+    return Index / Elements;
+  return Mask[Index] == 0 ? 0 : 1;
+}
+
 // Checks whether the shuffle mask represents a vector transpose (VTRN) by
 // checking that pairs of elements in the shuffle mask represent the same index
 // in each vector, incrementing the expected index by 2 at each step.
 // e.g. For v1,v2 of type v4i32 a valid shuffle mask is: [0, 4, 2, 6]
 //  v1={a,b,c,d} => x=shufflevector v1, v2 shufflemask => x={a,e,c,g}
 //  v2={e,f,g,h}
 // WhichResult gives the offset for each element in the mask based on which
 // of the two results it belongs to.
if (M.size() != NumElts && M.size() != NumElts*2)
     return false;
 
   // If the mask is twice as long as the input vector then we need to check the
   // upper and lower parts of the mask with a matching value for WhichResult
   // FIXME: A mask with only even values will be rejected in case the first
   // element is undefined, e.g. [-1, 4, 2, 6] will be rejected, because only
   // M[0] is used to determine WhichResult
   for (unsigned i = 0; i < M.size(); i += NumElts) {
-    if (M.size() == NumElts * 2)
-      WhichResult = i / NumElts;
-    else
-      WhichResult = M[i] == 0 ? 0 : 1;
+    WhichResult = SelectPairHalf(NumElts, M, i);
     for (unsigned j = 0; j < NumElts; j += 2) {
       if ((M[i+j] >= 0 && (unsigned) M[i+j] != j + WhichResult) ||
           (M[i+j+1] >= 0 && (unsigned) M[i+j+1] != j + NumElts + WhichResult))
         return false;
     }
   }
 
   if (M.size() == NumElts*2)
static bool isVTRN_v_undef_Mask(ArrayRef<int> M, EVT VT, unsigned &WhichResult){
   if (EltSz == 64)
     return false;
 
   unsigned NumElts = VT.getVectorNumElements();
   if (M.size() != NumElts && M.size() != NumElts*2)
     return false;
 
   for (unsigned i = 0; i < M.size(); i += NumElts) {
-    if (M.size() == NumElts * 2)
-      WhichResult = i / NumElts;
-    else
-      WhichResult = M[i] == 0 ? 0 : 1;
+    WhichResult = SelectPairHalf(NumElts, M, i);
     for (unsigned j = 0; j < NumElts; j += 2) {
       if ((M[i+j] >= 0 && (unsigned) M[i+j] != j + WhichResult) ||
           (M[i+j+1] >= 0 && (unsigned) M[i+j+1] != j + WhichResult))
         return false;
     }
   }
 
   if (M.size() == NumElts*2)
static bool isVUZPMask(ArrayRef<int> M, EVT VT, unsigned &WhichResult) {
   if (EltSz == 64)
     return false;
 
   unsigned NumElts = VT.getVectorNumElements();
   if (M.size() != NumElts && M.size() != NumElts*2)
     return false;
 
   for (unsigned i = 0; i < M.size(); i += NumElts) {
-    if (M.size() == NumElts * 2)
-      WhichResult = i / NumElts;
-    else
-      WhichResult = M[i] == 0 ? 0 : 1;
+    WhichResult = SelectPairHalf(NumElts, M, i);
     for (unsigned j = 0; j < NumElts; ++j) {
       if (M[i+j] >= 0 && (unsigned) M[i+j] != 2 * j + WhichResult)
         return false;
     }
   }
 
   if (M.size() == NumElts*2)
     WhichResult = 0;
if (EltSz == 64)
     return false;
 
   unsigned NumElts = VT.getVectorNumElements();
   if (M.size() != NumElts && M.size() != NumElts*2)
     return false;
 
   unsigned Half = NumElts / 2;
   for (unsigned i = 0; i < M.size(); i += NumElts) {
-    if (M.size() == NumElts * 2)
-      WhichResult = i / NumElts;
-    else
-      WhichResult = M[i] == 0 ? 0 : 1;
+    WhichResult = SelectPairHalf(NumElts, M, i);
     for (unsigned j = 0; j < NumElts; j += Half) {
       unsigned Idx = WhichResult;
       for (unsigned k = 0; k < Half; ++k) {
         int MIdx = M[i + j + k];
         if (MIdx >= 0 && (unsigned) MIdx != Idx)
           return false;
         Idx += 2;
       }
static bool isVZIPMask(ArrayRef<int> M, EVT VT, unsigned &WhichResult) {
   if (EltSz == 64)
     return false;
 
   unsigned NumElts = VT.getVectorNumElements();
   if (M.size() != NumElts && M.size() != NumElts*2)
     return false;
 
   for (unsigned i = 0; i < M.size(); i += NumElts) {
-    if (M.size() == NumElts * 2)
-      WhichResult = i / NumElts;
-    else
-      WhichResult = M[i] == 0 ? 0 : 1;
+    WhichResult = SelectPairHalf(NumElts, M, i);
     unsigned Idx = WhichResult * NumElts / 2;
     for (unsigned j = 0; j < NumElts; j += 2) {
       if ((M[i+j] >= 0 && (unsigned) M[i+j] != Idx) ||
           (M[i+j+1] >= 0 && (unsigned) M[i+j+1] != Idx + NumElts))
         return false;
       Idx += 1;
     }
   }
static bool isVZIP_v_undef_Mask(ArrayRef<int> M, EVT VT, unsigned &WhichResult){
   if (EltSz == 64)
     return false;
 
   unsigned NumElts = VT.getVectorNumElements();
   if (M.size() != NumElts && M.size() != NumElts*2)
     return false;
 
   for (unsigned i = 0; i < M.size(); i += NumElts) {
-    if (M.size() == NumElts * 2)
-      WhichResult = i / NumElts;
-    else
-      WhichResult = M[i] == 0 ? 0 : 1;
+    WhichResult = SelectPairHalf(NumElts, M, i);
     unsigned Idx = WhichResult * NumElts / 2;
     for (unsigned j = 0; j < NumElts; j += 2) {
       if ((M[i+j] >= 0 && (unsigned) M[i+j] != Idx) ||
           (M[i+j+1] >= 0 && (unsigned) M[i+j+1] != Idx))
         return false;
       Idx += 1;
     }
   }