[mlir][spirv] Add support to convert std.splat op

mlir/lib/Conversion/StandardToSPIRV/StandardToSPIRV.cpp

 class SelectOpPattern final : public OpConversionPattern<SelectOp> {
 public:
   using OpConversionPattern<SelectOp>::OpConversionPattern;
   LogicalResult
   matchAndRewrite(SelectOp op, ArrayRef<Value> operands,
                   ConversionPatternRewriter &rewriter) const override;
 };
 
+/// Converts std.splat to spv.CompositeConstruct.
+class SplatPattern final : public OpConversionPattern<SplatOp> {
+public:
+  using OpConversionPattern<SplatOp>::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(SplatOp op, ArrayRef<Value> operands,
+                  ConversionPatternRewriter &rewriter) const override;
+};
+
 /// Converts memref.store to spv.Store on integers.
 class IntStoreOpPattern final : public OpConversionPattern<memref::StoreOp> {
 public:
   using OpConversionPattern<memref::StoreOp>::OpConversionPattern;
 
   LogicalResult
   matchAndRewrite(memref::StoreOp storeOp, ArrayRef<Value> operands,
                   ConversionPatternRewriter &rewriter) const override;
SelectOpPattern::matchAndRewrite(SelectOp op, ArrayRef<Value> operands,
   SelectOpAdaptor selectOperands(operands);
   rewriter.replaceOpWithNewOp<spirv::SelectOp>(op, selectOperands.condition(),
                                                selectOperands.true_value(),
                                                selectOperands.false_value());
   return success();
 }
 
 //===----------------------------------------------------------------------===//
+// SplatOp
+//===----------------------------------------------------------------------===//
+
+LogicalResult
+SplatPattern::matchAndRewrite(SplatOp op, ArrayRef<Value> operands,
+                              ConversionPatternRewriter &rewriter) const {
+  auto dstVecType = op.getType().dyn_cast<VectorType>();
+  if (!dstVecType || !spirv::CompositeType::isValid(dstVecType))
+    return failure();
+  SplatOp::Adaptor adaptor(operands);
+  SmallVector<Value, 4> source(dstVecType.getNumElements(), adaptor.input());
+  rewriter.replaceOpWithNewOp<spirv::CompositeConstructOp>(op, dstVecType,
+                                                           source);
+  return success();
+}
+
+//===----------------------------------------------------------------------===//
 // StoreOp
 //===----------------------------------------------------------------------===//
 
 LogicalResult
 IntStoreOpPattern::matchAndRewrite(memref::StoreOp storeOp,
                                    ArrayRef<Value> operands,
                                    ConversionPatternRewriter &rewriter) const {
   memref::StoreOpAdaptor storeOperands(operands);
patterns.add<
 
       // Constant patterns
       ConstantCompositeOpPattern, ConstantScalarOpPattern,
 
       // Memory patterns
       AllocOpPattern, DeallocOpPattern, IntLoadOpPattern, IntStoreOpPattern,
       LoadOpPattern, StoreOpPattern,
 
-      ReturnOpPattern, SelectOpPattern,
+      ReturnOpPattern, SelectOpPattern, SplatPattern,
 
       // Type cast patterns
       UIToFPI1Pattern, ZeroExtendI1Pattern, TruncI1Pattern,
       TypeCastingOpPattern<IndexCastOp, spirv::SConvertOp>,
       TypeCastingOpPattern<SIToFPOp, spirv::ConvertSToFOp>,
       TypeCastingOpPattern<UIToFPOp, spirv::ConvertUToFOp>,
       TypeCastingOpPattern<SignExtendIOp, spirv::SConvertOp>,
       TypeCastingOpPattern<ZeroExtendIOp, spirv::UConvertOp>,

mlir/test/Conversion/StandardToSPIRV/std-ops-to-spirv.mlir

func @tensor_extract_constant(%a : index, %b: index, %c: index) -> i32 {
   // CHECK: %[[MUL2:.+]] = spv.IMul %[[C1]], %[[C]] : i32
   // CHECK: %[[ADD2:.+]] = spv.IAdd %[[ADD1]], %[[MUL2]] : i32
   // CHECK: %[[AC:.+]] = spv.AccessChain %[[VAR]][%[[ADD2]]]
   // CHECK: %[[VAL:.+]] = spv.Load "Function" %[[AC]] : i32
   %extract = tensor.extract %cst[%a, %b, %c] : tensor<2x2x3xi32>
   // CHECK: spv.ReturnValue %[[VAL]]
   return %extract : i32
 }
+
+// -----
+
+//===----------------------------------------------------------------------===//
+// splat
+//===----------------------------------------------------------------------===//
+
+// CHECK-LABEL: func @splat
+//  CHECK-SAME: (%[[A:.+]]: f32)
+//       CHECK:   %[[VAL:.+]] = spv.CompositeConstruct %[[A]], %[[A]], %[[A]], %[[A]] : vector<4xf32>
+//       CHECK:   spv.ReturnValue %[[VAL]]
+func @splat(%f : f32) -> vector<4xf32> {
+  %splat = splat %f : vector<4xf32>
+  return %splat : vector<4xf32>
+}