Revert "Add validation of vloada_half instruction (#1138)"

This reverts commit 1a7f142.

The vloada_halfn functions return float vectors:

   floatn vloada_halfn(size_t offset, const __global half *p)
   floatn vloada_halfn(size_t offset, const __local half *p)
   floatn vloada_halfn(size_t offset, const __constant half *p)
   floatn vloada_halfn(size_t offset, const __private half *p)

   For the generic address space:
   floatn vloada_halfn(size_t offset, const half *p)

These functions exist specifically for implementations that lack the
cl_khr_fp16 extension, and so do not include the halfn vector types,
but do include a scalar half type for use as a pointer argument *only*.

Likewise, in the SPIR-V OpenCL Extended Instruction Set, the result type
for vloada_halfn is defined as follows:

   Result Type must be vector(2,3,4,8,16) of float values.

The assertion added to isBuiltinTransToExtInst(...) is therefore
incorrect.

The vloada_halfn SPIR-V OpenCL Extended Instruction Set instructions
that are emitted for calls to these builtins are accepted by the
SPIR-V Validator.

Author: StuartDBrady

lib/SPIRV/SPIRVToOCL.cpp

@@ -982,8 +982,6 @@ void SPIRVToOCLBase::visitCallSPIRVVLoadn(CallInst *CI, OCLExtOpKind Kind) {
         std::string Name = OCLExtOpMap::map(Kind);
         if (ConstantInt *C = dyn_cast<ConstantInt>(Args.back())) {
           uint64_t NumComponents = C->getZExtValue();
-          assert(NumComponents > 1 &&
-                 "vloada_halfn instruction is not for scalar types");
           std::stringstream SS;
           SS << NumComponents;
           Name.replace(Name.find("n"), 1, SS.str());

lib/SPIRV/SPIRVWriter.cpp

@@ -208,16 +208,6 @@ bool LLVMToSPIRVBase::isBuiltinTransToExtInst(
   OCLExtOpKind EOC;
   if (!OCLExtOpMap::rfind(Splited.first.str(), &EOC))
     return false;
-  if (EOC == OpenCLLIB::Vloada_halfn) {
-    auto *VecTy = dyn_cast<VectorType>(F->getReturnType());
-    if (!VecTy)
-      BM->getErrorLog().checkError(
-          false, SPIRVEC_InvalidModule,
-          "vloada_half should be of a half vector type");
-    auto *Ty = VecTy->getElementType();
-    BM->getErrorLog().checkError(Ty->isHalfTy(), SPIRVEC_InvalidModule,
-                                 "vloada_half should be of a half vector type");
-  }
 
   if (ExtSet)
     *ExtSet = Set;