[VFABI] Create FunctionType for vector functions (#75058)

`createFunctionType` returns a FunctionType  that may contain a mask,
which is currently placed as the last parameter to the Function.
The placement happens according to `VFParameters` of `VFInfo`, and it
should be able to handle VFABI specification changes.

Regarding the return type, it uses the scalar type of the input instruction,
as the specification does not encode in the mangled name such information.
If that ever happens, that information should be available from `VFInfo`.

Author: paschalis-mpeis

llvm/include/llvm/Analysis/VectorUtils.h

@@ -195,6 +195,16 @@ static constexpr char const *MappingsAttrName = "vector-function-abi-variant";
 /// the presence of the attribute (see InjectTLIMappings).
 void getVectorVariantNames(const CallInst &CI,
                            SmallVectorImpl<std::string> &VariantMappings);
+
+/// Constructs a FunctionType by applying vector function information to the
+/// type of a matching scalar function.
+/// \param Info gets the vectorization factor (VF) and the VFParamKind of the
+/// parameters.
+/// \param ScalarFTy gets the Type information of parameters, as it is not
+/// stored in \p Info.
+/// \returns a pointer to a newly created vector FunctionType
+FunctionType *createFunctionType(const VFInfo &Info,
+                                 const FunctionType *ScalarFTy);
 } // end namespace VFABI
 
 /// The Vector Function Database.

llvm/lib/Analysis/VFABIDemangling.cpp

@@ -376,7 +376,7 @@ std::optional<VFInfo> VFABI::tryDemangleForVFABI(StringRef MangledName,
   // _ZGV<isa><mask><vlen><parameters>_<scalarname>.
   StringRef VectorName = MangledName;
 
-  // Parse the fixed size part of the manled name
+  // Parse the fixed size part of the mangled name
   if (!MangledName.consume_front("_ZGV"))
     return std::nullopt;
 

llvm/lib/Analysis/VectorUtils.cpp

@@ -12,6 +12,7 @@
 
 #include "llvm/Analysis/VectorUtils.h"
 #include "llvm/ADT/EquivalenceClasses.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/Analysis/DemandedBits.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/LoopIterator.h"
@@ -20,6 +21,7 @@
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/Constants.h"
+#include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/PatternMatch.h"
 #include "llvm/IR/Value.h"
@@ -1477,6 +1479,32 @@ void VFABI::getVectorVariantNames(
   }
 }
 
+FunctionType *VFABI::createFunctionType(const VFInfo &Info,
+                                        const FunctionType *ScalarFTy) {
+  // Create vector parameter types
+  SmallVector<Type *, 8> VecTypes;
+  ElementCount VF = Info.Shape.VF;
+  int ScalarParamIndex = 0;
+  for (auto VFParam : Info.Shape.Parameters) {
+    if (VFParam.ParamKind == VFParamKind::GlobalPredicate) {
+      VectorType *MaskTy =
+          VectorType::get(Type::getInt1Ty(ScalarFTy->getContext()), VF);
+      VecTypes.push_back(MaskTy);
+      continue;
+    }
+
+    Type *OperandTy = ScalarFTy->getParamType(ScalarParamIndex++);
+    if (VFParam.ParamKind == VFParamKind::Vector)
+      OperandTy = VectorType::get(OperandTy, VF);
+    VecTypes.push_back(OperandTy);
+  }
+
+  auto *RetTy = ScalarFTy->getReturnType();
+  if (!RetTy->isVoidTy())
+    RetTy = VectorType::get(RetTy, VF);
+  return FunctionType::get(RetTy, VecTypes, false);
+}
+
 bool VFShape::hasValidParameterList() const {
   for (unsigned Pos = 0, NumParams = Parameters.size(); Pos < NumParams;
        ++Pos) {