[clang] [CIR] Add if statement support (PR #134333)

[Andy Kaylor via cfe-commits]

================
@@ -447,6 +448,133 @@ mlir::LogicalResult cir::ReturnOp::verify() {
   return success();
 }
 
+//===----------------------------------------------------------------------===//
+// IfOp
+//===----------------------------------------------------------------------===//
+
+ParseResult cir::IfOp::parse(OpAsmParser &parser, OperationState &result) {
+  // create the regions for 'then'.
+  result.regions.reserve(2);
+  Region *thenRegion = result.addRegion();
+  Region *elseRegion = result.addRegion();
+
+  mlir::Builder &builder = parser.getBuilder();
+  OpAsmParser::UnresolvedOperand cond;
+  Type boolType = cir::BoolType::get(builder.getContext());
+
+  if (parser.parseOperand(cond) ||
+      parser.resolveOperand(cond, boolType, result.operands))
+    return failure();
+
+  // Parse 'then' region.
+  mlir::SMLoc parseThenLoc = parser.getCurrentLocation();
+  if (parser.parseRegion(*thenRegion, /*arguments=*/{}, /*argTypes=*/{}))
+    return failure();
+
+  if (ensureRegionTerm(parser, *thenRegion, parseThenLoc).failed())
+    return failure();
+
+  // If we find an 'else' keyword, parse the 'else' region.
+  if (!parser.parseOptionalKeyword("else")) {
+    mlir::SMLoc parseElseLoc = parser.getCurrentLocation();
+    if (parser.parseRegion(*elseRegion, /*arguments=*/{}, /*argTypes=*/{}))
+      return failure();
+    if (ensureRegionTerm(parser, *elseRegion, parseElseLoc).failed())
+      return failure();
+  }
+
+  // Parse the optional attribute list.
+  if (parser.parseOptionalAttrDict(result.attributes))
+    return failure();
+  return success();
+}
+
+void cir::IfOp::print(OpAsmPrinter &p) {
+
+  p << " " << getCondition() << " ";
+  mlir::Region &thenRegion = this->getThenRegion();
+  p.printRegion(thenRegion,
+                /*printEntryBlockArgs=*/false,
+                /*printBlockTerminators=*/!omitRegionTerm(thenRegion));
+
+  // Print the 'else' regions if it exists and has a block.
+  mlir::Region &elseRegion = this->getElseRegion();
+  if (!elseRegion.empty()) {
+    p << " else ";
+    p.printRegion(elseRegion,
+                  /*printEntryBlockArgs=*/false,
+                  /*printBlockTerminators=*/!omitRegionTerm(elseRegion));
+  }
+
+  p.printOptionalAttrDict(getOperation()->getAttrs());
+}
+
+/// Default callback for IfOp builders.
+void cir::buildTerminatedBody(OpBuilder &builder, Location loc) {
+  // add cir.yield to end of the block
+  builder.create<cir::YieldOp>(loc);
+}
+
+/// Given the region at `index`, or the parent operation if `index` is None,
+/// return the successor regions. These are the regions that may be selected
+/// during the flow of control. `operands` is a set of optional attributes that
+/// correspond to a constant value for each operand, or null if that operand is
+/// not a constant.
+void cir::IfOp::getSuccessorRegions(mlir::RegionBranchPoint point,
+                                    SmallVectorImpl<RegionSuccessor> &regions) {
+  // The `then` and the `else` region branch back to the parent operation.
+  if (!point.isParent()) {
+    regions.push_back(RegionSuccessor());
+    return;
+  }
+
+  // Don't consider the else region if it is empty.
+  Region *elseRegion = &this->getElseRegion();
+  if (elseRegion->empty())
+    elseRegion = nullptr;
+
+  // Otherwise, the successor is dependent on the condition.
+  // bool condition;
+  // if (auto condAttr = operands.front().dyn_cast_or_null<IntegerAttr>()) {
----------------
andykaylor wrote:

I'm not sure what this code was doing or when it was commented out. It should be removed.

https://github.com/llvm/llvm-project/pull/134333