[CIR] Backport VecSplatOp simplifier (#1704)

Backporting the VecSplatOp simplifier from the upstream

Author: AmrDeveloper

clang/lib/CIR/Dialect/Transforms/CIRSimplify.cpp

@@ -141,6 +141,31 @@ struct SimplifySelect : public OpRewritePattern<SelectOp> {
   }
 };
 
+struct SimplifyVecSplat : public OpRewritePattern<VecSplatOp> {
+  using OpRewritePattern<VecSplatOp>::OpRewritePattern;
+  LogicalResult matchAndRewrite(VecSplatOp op,
+                                PatternRewriter &rewriter) const override {
+    mlir::Value splatValue = op.getValue();
+    auto constant =
+        mlir::dyn_cast_if_present<cir::ConstantOp>(splatValue.getDefiningOp());
+    if (!constant)
+      return mlir::failure();
+
+    auto value = constant.getValue();
+    if (!mlir::isa_and_nonnull<cir::IntAttr>(value) &&
+        !mlir::isa_and_nonnull<cir::FPAttr>(value))
+      return mlir::failure();
+
+    cir::VectorType resultType = op.getResult().getType();
+    SmallVector<mlir::Attribute, 16> elements(resultType.getSize(), value);
+    auto constVecAttr = cir::ConstVectorAttr::get(
+        resultType, mlir::ArrayAttr::get(getContext(), elements));
+
+    rewriter.replaceOpWithNewOp<cir::ConstantOp>(op, constVecAttr);
+    return mlir::success();
+  }
+};
+
 //===----------------------------------------------------------------------===//
 // CIRSimplifyPass
 //===----------------------------------------------------------------------===//
@@ -155,7 +180,8 @@ void populateMergeCleanupPatterns(RewritePatternSet &patterns) {
   // clang-format off
   patterns.add<
     SimplifyTernary,
-    SimplifySelect
+    SimplifySelect,
+    SimplifyVecSplat
   >(patterns.getContext());
   // clang-format on
 }
@@ -168,7 +194,7 @@ void CIRSimplifyPass::runOnOperation() {
   // Collect operations to apply patterns.
   llvm::SmallVector<Operation *, 16> ops;
   getOperation()->walk([&](Operation *op) {
-    if (isa<TernaryOp, SelectOp>(op))
+    if (isa<TernaryOp, SelectOp, VecSplatOp>(op))
       ops.push_back(op);
   });
 

clang/test/CIR/Transforms/vector-splat.cir

@@ -0,0 +1,16 @@
+// RUN: cir-opt %s -cir-simplify -o - | FileCheck %s
+
+!s32i = !cir.int<s, 32>
+
+module  {
+  cir.func @fold_splat_vector_op_test() -> !cir.vector<!s32i x 4> {
+    %v = cir.const #cir.int<3> : !s32i
+    %vec = cir.vec.splat %v : !s32i, !cir.vector<!s32i x 4>
+    cir.return %vec : !cir.vector<!s32i x 4>
+  }
+
+  // CHECK: cir.func @fold_splat_vector_op_test() -> !cir.vector<!s32i x 4> {
+  // CHECK-NEXT: %0 = cir.const #cir.const_vector<[#cir.int<3> : !s32i, #cir.int<3> : !s32i,
+  // CHECK-SAME: #cir.int<3> : !s32i, #cir.int<3> : !s32i]> : !cir.vector<!s32i x 4>
+  // CHECK-NEXT: cir.return %0 : !cir.vector<!s32i x 4>
+}