[CIR][CIRGen][NFC] Exceptions: add cleanups to cir.call

Now that the basic is working, start adding cleanups to be attached to
cir.call's instead. This is necessary in order to tie the pieces
(landing pads and cleanups) more properly, allowing multiple calls
inside cir.try op to be connected with the right cleanup.

This is the first piece of a series, tests coming next.

Author: bcardosolopes

clang/include/clang/CIR/Dialect/IR/CIROps.td

@@ -3226,7 +3226,7 @@ class CIR_CallOp<string mnemonic, list<Trait> extra_traits = []> :
   );
 }
 
-def CallOp : CIR_CallOp<"call"> {
+def CallOp : CIR_CallOp<"call", [NoRegionArguments]> {
   let summary = "call operation";
   let description = [{
     Direct and indirect calls.
@@ -3241,7 +3241,9 @@ def CallOp : CIR_CallOp<"call"> {
     Given the way indirect calls are encoded, avoid using `mlir::Operation`
     methods to walk the operands for this operation, instead use the methods
     provided by `CIRCallOpInterface`.
-    ``
+
+    If the `cir.call` has the `exception` keyword, the call can throw. In this
+    case, cleanups can be added in the `cleanup` region.
 
     Example:
 
@@ -3251,13 +3253,19 @@ def CallOp : CIR_CallOp<"call"> {
      ...
     // Indirect call
     %20 = cir.call %18(%17)
+     ...
+    // Call that might throw
+    cir.call exception @my_div() -> () cleanup {
+      // call dtor...
+    }
     ```
   }];
 
   let results = (outs Optional<CIR_AnyType>:$result);
   let arguments = !con((ins
     UnitAttr:$exception
   ), commonArgs);
+  let regions = (region AnyRegion:$cleanup);
 
   let skipDefaultBuilders = 1;
 
@@ -3275,6 +3283,8 @@ def CallOp : CIR_CallOp<"call"> {
         $_state.addAttribute("exception", exception);
       if (resType && !isa<VoidType>(resType))
         $_state.addTypes(resType);
+      // Create region placeholder for potential cleanups.
+      $_state.addRegion();
     }]>,
     OpBuilder<(ins "Value":$ind_target,
                "FuncType":$fn_type,
@@ -3289,6 +3299,8 @@ def CallOp : CIR_CallOp<"call"> {
         CallingConvAttr::get($_builder.getContext(), callingConv));
       if (exception)
         $_state.addAttribute("exception", exception);
+      // Create region placeholder for potential cleanups.
+      $_state.addRegion();
     }]>
   ];
 }

clang/lib/CIR/Dialect/IR/CIRDialect.cpp

@@ -2822,8 +2822,11 @@ static ::mlir::ParseResult parseCallCommon(::mlir::OpAsmParser &parser,
   llvm::SMLoc landingPadOperandsLoc;
   llvm::SmallVector<mlir::Type, 1> landingPadTypes;
 
-  if (::mlir::succeeded(parser.parseOptionalKeyword("exception")))
+  bool hasExceptions = false;
+  if (::mlir::succeeded(parser.parseOptionalKeyword("exception"))) {
     result.addAttribute("exception", parser.getBuilder().getUnitAttr());
+    hasExceptions = true;
+  }
 
   // If we cannot parse a string callee, it means this is an indirect call.
   if (!parser.parseOptionalAttribute(calleeAttr, "callee", result.attributes)
@@ -2910,6 +2913,18 @@ static ::mlir::ParseResult parseCallCommon(::mlir::OpAsmParser &parser,
                                             builder.getContext(), callingConv));
   }
 
+  // If exception is present and there are cleanups, this should be latest thing
+  // present (after all attributes, etc).
+  mlir::Region *cleanupRegion = nullptr;
+  if (!hasDestinationBlocks) // Regular cir.call
+    cleanupRegion = result.addRegion();
+  if (hasExceptions) {
+    if (parser.parseOptionalKeyword("cleanup").succeeded()) {
+      if (parser.parseRegion(*cleanupRegion, /*arguments=*/{}, /*argTypes=*/{}))
+        return failure();
+    }
+  }
+
   return ::mlir::success();
 }
 
@@ -2989,6 +3004,17 @@ void printCallCommon(Operation *op, mlir::Value indirectCallee,
     state.printAttributeWithoutType(extraAttrs);
     state << ")";
   }
+
+  // If exception is present and there are cleanups, this should be latest thing
+  // present (after all attributes, etc).
+  if (exception) {
+    auto call = dyn_cast<mlir::cir::CallOp>(op);
+    assert(call && "expected regular call");
+    if (!call.getCleanup().empty()) {
+      state << "cleanup ";
+      state.printRegion(call.getCleanup());
+    }
+  }
 }
 
 LogicalResult