[ValueTypes] Rename MVT::getVectorNumElements() to MVT::getVectorMinNumElements(). Fix some misuses of getVectorNumElements()

getVectorNumElements() returns a value for scalable vectors
without any warning so it is effectively getVectorMinNumElements().
By renaming it and making getVectorNumElements() forward to
it, we can insert a check for scalable vectors into getVectorNumElements()
similar to EVT. I didn't do that in this patch because there are still more
fixes needed, but I was able to temporarily do it and passed the RISCV
lit tests with these changes.

The changes to isPow2VectorType and getPow2VectorType are copied from EVT.

The change to TypeInfer::EnforceSameNumElts reduces the size of AArch64's isel table.
We're now considering SameNumElts to require the scalable property to match which
removes some unneeded type checks.

This was motivated by the bug I fixed yesterday in 80b9510806cf11c57f2dd87191d3989fc45defa8

Reviewed By: frasercrmck, sdesmalen

Differential Revision: https://reviews.llvm.org/D102262

include/llvm/Support/MachineValueType.h

@@ -478,7 +478,7 @@ namespace llvm {
 
     /// Returns true if the given vector is a power of 2.
     bool isPow2VectorType() const {
-      unsigned NElts = getVectorNumElements();
+      unsigned NElts = getVectorMinNumElements();
       return !(NElts & (NElts - 1));
     }
 
@@ -488,9 +488,10 @@ namespace llvm {
       if (isPow2VectorType())
         return *this;
 
-      unsigned NElts = getVectorNumElements();
-      unsigned Pow2NElts = 1 << Log2_32_Ceil(NElts);
-      return MVT::getVectorVT(getVectorElementType(), Pow2NElts);
+      ElementCount NElts = getVectorElementCount();
+      unsigned NewMinCount = 1 << Log2_32_Ceil(NElts.getKnownMinValue());
+      NElts = ElementCount::get(NewMinCount, NElts.isScalable());
+      return MVT::getVectorVT(getVectorElementType(), NElts);
     }
 
     /// If this is a vector, return the element type, otherwise return this.
@@ -651,7 +652,8 @@ namespace llvm {
       }
     }
 
-    unsigned getVectorNumElements() const {
+    /// Given a vector type, return the minimum number of elements it contains.
+    unsigned getVectorMinNumElements() const {
       switch (SimpleTy) {
       default:
         llvm_unreachable("Not a vector MVT!");
@@ -805,12 +807,12 @@ namespace llvm {
     }
 
     ElementCount getVectorElementCount() const {
-      return ElementCount::get(getVectorNumElements(), isScalableVector());
+      return ElementCount::get(getVectorMinNumElements(), isScalableVector());
     }
 
-    /// Given a vector type, return the minimum number of elements it contains.
-    unsigned getVectorMinNumElements() const {
-      return getVectorElementCount().getKnownMinValue();
+    unsigned getVectorNumElements() const {
+      // TODO: Check that this isn't a scalable vector.
+      return getVectorMinNumElements();
     }
 
     /// Returns the size of the specified MVT in bits.

lib/Target/AMDGPU/SIISelLowering.cpp

@@ -1568,8 +1568,8 @@ bool SITargetLowering::isMemOpUniform(const SDNode *N) const {
 
 TargetLoweringBase::LegalizeTypeAction
 SITargetLowering::getPreferredVectorAction(MVT VT) const {
-  int NumElts = VT.getVectorNumElements();
-  if (NumElts != 1 && VT.getScalarType().bitsLE(MVT::i16))
+  if (!VT.isScalableVector() && VT.getVectorNumElements() != 1 &&
+      VT.getScalarType().bitsLE(MVT::i16))
     return VT.isPow2VectorType() ? TypeSplitVector : TypeWidenVector;
   return TargetLoweringBase::getPreferredVectorAction(VT);
 }

lib/Target/Hexagon/HexagonISelLowering.cpp

@@ -2101,7 +2101,7 @@ bool HexagonTargetLowering::isShuffleMaskLegal(ArrayRef<int> Mask,
 
 TargetLoweringBase::LegalizeTypeAction
 HexagonTargetLowering::getPreferredVectorAction(MVT VT) const {
-  unsigned VecLen = VT.getVectorNumElements();
+  unsigned VecLen = VT.getVectorMinNumElements();
   MVT ElemTy = VT.getVectorElementType();
 
   if (VecLen == 1 || VT.isScalableVector())

lib/Target/NVPTX/NVPTXISelLowering.cpp

@@ -1175,7 +1175,8 @@ const char *NVPTXTargetLowering::getTargetNodeName(unsigned Opcode) const {
 
 TargetLoweringBase::LegalizeTypeAction
 NVPTXTargetLowering::getPreferredVectorAction(MVT VT) const {
-  if (VT.getVectorNumElements() != 1 && VT.getScalarType() == MVT::i1)
+  if (!VT.isScalableVector() && VT.getVectorNumElements() != 1 &&
+      VT.getScalarType() == MVT::i1)
     return TypeSplitVector;
   if (VT == MVT::v2f16)
     return TypeLegal;

lib/Target/PowerPC/PPCISelLowering.h

@@ -742,7 +742,8 @@ namespace llvm {
     /// then the VPERM for the shuffle. All in all a very slow sequence.
     TargetLoweringBase::LegalizeTypeAction getPreferredVectorAction(MVT VT)
       const override {
-      if (VT.getVectorNumElements() != 1 && VT.getScalarSizeInBits() % 8 == 0)
+      if (!VT.isScalableVector() && VT.getVectorNumElements() != 1 &&
+          VT.getScalarSizeInBits() % 8 == 0)
         return TypeWidenVector;
       return TargetLoweringBase::getPreferredVectorAction(VT);
     }

lib/Target/X86/X86ISelLowering.cpp

@@ -2101,7 +2101,7 @@ X86TargetLowering::getPreferredVectorAction(MVT VT) const {
       !Subtarget.hasBWI())
     return TypeSplitVector;
 
-  if (VT.getVectorNumElements() != 1 &&
+  if (!VT.isScalableVector() && VT.getVectorNumElements() != 1 &&
       VT.getVectorElementType() != MVT::i1)
     return TypeWidenVector;
 

utils/TableGen/CodeGenDAGPatterns.cpp

@@ -630,7 +630,7 @@ bool TypeInfer::EnforceVectorSubVectorTypeIs(TypeSetByHwMode &Vec,
       return false;
     if (B.getVectorElementType() != P.getVectorElementType())
       return false;
-    return B.getVectorNumElements() < P.getVectorNumElements();
+    return B.getVectorMinNumElements() < P.getVectorMinNumElements();
   };
 
   /// Return true if S has no element (vector type) that T is a sub-vector of,
@@ -696,8 +696,10 @@ bool TypeInfer::EnforceSameNumElts(TypeSetByHwMode &V, TypeSetByHwMode &W) {
   // An actual vector type cannot have 0 elements, so we can treat scalars
   // as zero-length vectors. This way both vectors and scalars can be
   // processed identically.
-  auto NoLength = [](const SmallSet<unsigned,2> &Lengths, MVT T) -> bool {
-    return !Lengths.count(T.isVector() ? T.getVectorNumElements() : 0);
+  auto NoLength = [](const SmallDenseSet<ElementCount> &Lengths,
+                     MVT T) -> bool {
+    return !Lengths.count(T.isVector() ? T.getVectorElementCount()
+                                       : ElementCount::getNull());
   };
 
   SmallVector<unsigned, 4> Modes;
@@ -706,11 +708,13 @@ bool TypeInfer::EnforceSameNumElts(TypeSetByHwMode &V, TypeSetByHwMode &W) {
     TypeSetByHwMode::SetType &VS = V.get(M);
     TypeSetByHwMode::SetType &WS = W.get(M);
 
-    SmallSet<unsigned,2> VN, WN;
+    SmallDenseSet<ElementCount> VN, WN;
     for (MVT T : VS)
-      VN.insert(T.isVector() ? T.getVectorNumElements() : 0);
+      VN.insert(T.isVector() ? T.getVectorElementCount()
+                             : ElementCount::getNull());
     for (MVT T : WS)
-      WN.insert(T.isVector() ? T.getVectorNumElements() : 0);
+      WN.insert(T.isVector() ? T.getVectorElementCount()
+                             : ElementCount::getNull());
 
     Changed |= berase_if(VS, std::bind(NoLength, WN, std::placeholders::_1));
     Changed |= berase_if(WS, std::bind(NoLength, VN, std::placeholders::_1));

utils/TableGen/IntrinsicEmitter.cpp

@@ -378,7 +378,7 @@ static void EncodeFixedType(Record *R, std::vector<unsigned char> &ArgCodes,
     MVT VVT = VT;
     if (VVT.isScalableVector())
       Sig.push_back(IIT_SCALABLE_VEC);
-    switch (VVT.getVectorNumElements()) {
+    switch (VVT.getVectorMinNumElements()) {
     default: PrintFatalError("unhandled vector type width in intrinsic!");
     case 1: Sig.push_back(IIT_V1); break;
     case 2: Sig.push_back(IIT_V2); break;