[clang] [CIR] Upstream initial support for switch statements (PR #137106)

[Henrich Lauko via cfe-commits]

================
@@ -802,6 +804,132 @@ Block 
*cir::BrCondOp::getSuccessorForOperands(ArrayRef<Attribute> operands) {
   return nullptr;
 }
 
+//===----------------------------------------------------------------------===//
+// CaseOp
+//===----------------------------------------------------------------------===//
+
+void cir::CaseOp::getSuccessorRegions(
+    mlir::RegionBranchPoint point, SmallVectorImpl<RegionSuccessor> &regions) {
+  if (!point.isParent()) {
+    regions.push_back(RegionSuccessor());
+    return;
+  }
+  regions.push_back(RegionSuccessor(&getCaseRegion()));
+}
+
+void cir::CaseOp::build(OpBuilder &builder, OperationState &result,
+                        ArrayAttr value, CaseOpKind kind,
+                        OpBuilder::InsertPoint &insertPoint) {
+  OpBuilder::InsertionGuard guardSwitch(builder);
+  result.addAttribute("value", value);
+  result.getOrAddProperties<Properties>().kind =
+      cir::CaseOpKindAttr::get(builder.getContext(), kind);
+  Region *caseRegion = result.addRegion();
+  builder.createBlock(caseRegion);
+
+  insertPoint = builder.saveInsertionPoint();
+}
+
+LogicalResult cir::CaseOp::verify() { return success(); }
+
+//===----------------------------------------------------------------------===//
+// SwitchOp
+//===----------------------------------------------------------------------===//
+
+static ParseResult parseSwitchOp(OpAsmParser &parser, mlir::Region &regions,
+                                 mlir::OpAsmParser::UnresolvedOperand &cond,
+                                 mlir::Type &condType) {
+  cir::IntType intCondType;
+
+  if (parser.parseLParen())
+    return ::mlir::failure();
+
+  if (parser.parseOperand(cond))
+    return ::mlir::failure();
+  if (parser.parseColon())
+    return ::mlir::failure();
+  if (parser.parseCustomTypeWithFallback(intCondType))
+    return ::mlir::failure();
+  condType = intCondType;
+
+  if (parser.parseRParen())
+    return ::mlir::failure();
+  if (parser.parseRegion(regions, /*arguments=*/{}, /*argTypes=*/{}))
+    return failure();
+
+  return ::mlir::success();
+}
+
+static void printSwitchOp(OpAsmPrinter &p, cir::SwitchOp op,
+                          mlir::Region &bodyRegion, mlir::Value condition,
+                          mlir::Type condType) {
+  p << "(";
+  p << condition;
+  p << " : ";
+  p.printStrippedAttrOrType(condType);
+  p << ")";
+
+  p << ' ';
+  p.printRegion(bodyRegion, /*printEntryBlockArgs=*/false,
+                /*printBlockTerminators=*/true);
+}
+
+void cir::SwitchOp::getSuccessorRegions(
+    mlir::RegionBranchPoint point, SmallVectorImpl<RegionSuccessor> &region) {
+  if (!point.isParent()) {
+    region.push_back(RegionSuccessor());
+    return;
+  }
+
+  region.push_back(RegionSuccessor(&getBody()));
+}
+
+LogicalResult cir::SwitchOp::verify() { return success(); }
+
+void cir::SwitchOp::build(
+    OpBuilder &builder, OperationState &result, Value cond,
+    function_ref<void(OpBuilder &, Location, OperationState &)> switchBuilder) 
{
+  assert(switchBuilder && "the builder callback for regions must be present");
+  OpBuilder::InsertionGuard guardSwitch(builder);
+  Region *switchRegion = result.addRegion();
+  builder.createBlock(switchRegion);
+  result.addOperands({cond});
+  switchBuilder(builder, result.location, result);
+}
+
+void cir::SwitchOp::collectCases(llvm::SmallVector<CaseOp> &cases) {
+  walk<mlir::WalkOrder::PreOrder>([&](mlir::Operation *op) {
+    // Don't walk in nested switch op.
+    if (isa<cir::SwitchOp>(op) && op != *this)
+      return WalkResult::skip();
+
+    if (auto caseOp = dyn_cast<cir::CaseOp>(op))
+      cases.push_back(caseOp);
+
+    return WalkResult::advance();
+  });
+}
+
+// Check if the switch is in a simple form. If yes, collect the cases to \param
+// cases. This is an expensive and need to be used with caution.
----------------
xlauko wrote:

This is not true as it collects cases also in the case it is not in simple form.

https://github.com/llvm/llvm-project/pull/137106
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