[CIR][NFC] Add cleanup region to ScopeOp

This does not change anything in practice, work in that direction should come
next. We also want this to not affect existing tests to isolate upcoming
changes.

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

@@ -1066,23 +1066,29 @@ def ScopeOp : CIR_Op<"scope", [
     The blocks can be terminated by `cir.yield`, `cir.return` or `cir.throw`.
     If `cir.scope` yields no value, the `cir.yield` can be left out, and
     will be inserted implicitly.
+
+    The scope might also have an associated `cleanup` region, providing code
+    that run destruction of automatic variables. Note that in order to lower the
+    cleanup region while keeping C++ semantics, all immediate control-flow
+    breaking operations not under a children scope should jump to this cleanup
+    code.
   }];
 
   let results = (outs Optional<CIR_AnyType>:$results);
-  let regions = (region AnyRegion:$scopeRegion);
+  let regions = (region AnyRegion:$scopeRegion, AnyRegion:$cleanupRegion);
 
   let hasVerifier = 1;
   let skipDefaultBuilders = 1;
   let assemblyFormat = [{
-    custom<OmittedTerminatorRegion>($scopeRegion) (`:` type($results)^)? attr-dict
+    custom<OmittedTerminatorRegion>($scopeRegion, $cleanupRegion) (`:` type($results)^)? attr-dict
   }];
 
   let extraClassDeclaration = [{
     /// Determine whether the scope is empty, meaning it contains a single block
     /// terminated by a cir.yield.
     bool isEmpty() {
-      auto &entry = getRegion().front();
-      return getRegion().hasOneBlock() &&
+      auto &entry = getScopeRegion().front();
+      return getScopeRegion().hasOneBlock() &&
         llvm::isa<YieldOp>(entry.front());
       }
     }];

clang/lib/CIR/CodeGen/CIRGenExpr.cpp

@@ -2842,7 +2842,7 @@ mlir::Value CIRGenFunction::emitAlloca(StringRef name, mlir::Type ty,
   if (auto tryOp =
           llvm::dyn_cast_if_present<cir::TryOp>(entryBlock->getParentOp())) {
     if (auto scopeOp = llvm::dyn_cast<cir::ScopeOp>(tryOp->getParentOp()))
-      entryBlock = &scopeOp.getRegion().front();
+      entryBlock = &scopeOp.getScopeRegion().front();
   }
 
   return emitAlloca(name, ty, loc, alignment,

clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp

@@ -826,13 +826,16 @@ void CIRGenItaniumCXXABI::emitBeginCatch(CIRGenFunction &CGF,
   auto getCatchParamAllocaIP = [&]() {
     auto currIns = CGF.getBuilder().saveInsertionPoint();
     auto currParent = currIns.getBlock()->getParentOp();
-    mlir::Operation *scopeLikeOp = currParent->getParentOfType<cir::ScopeOp>();
-    if (!scopeLikeOp)
-      scopeLikeOp = currParent->getParentOfType<cir::FuncOp>();
-    assert(scopeLikeOp && "unknown outermost scope-like parent");
-    assert(scopeLikeOp->getNumRegions() == 1 && "expected single region");
 
-    auto *insertBlock = &scopeLikeOp->getRegion(0).getBlocks().back();
+    mlir::Block *insertBlock = nullptr;
+    if (auto scopeOp = currParent->getParentOfType<cir::ScopeOp>()) {
+      insertBlock = &scopeOp.getScopeRegion().getBlocks().back();
+    } else if (auto fnOp = currParent->getParentOfType<cir::FuncOp>()) {
+      insertBlock = &fnOp.getRegion().getBlocks().back();
+    } else {
+      llvm_unreachable("unknown outermost scope-like parent");
+    }
+
     return CGF.getBuilder().getBestAllocaInsertPoint(insertBlock);
   };
 

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

@@ -276,22 +276,41 @@ void parseVisibilityAttr(OpAsmParser &parser, cir::VisibilityAttr &visibility) {
 // CIR Custom Parsers/Printers
 //===----------------------------------------------------------------------===//
 
-static mlir::ParseResult parseOmittedTerminatorRegion(mlir::OpAsmParser &parser,
-                                                      mlir::Region &region) {
+static mlir::ParseResult
+parseOmittedTerminatorRegion(mlir::OpAsmParser &parser,
+                             mlir::Region &scopeRegion,
+                             mlir::Region &cleanupRegion) {
   auto regionLoc = parser.getCurrentLocation();
-  if (parser.parseRegion(region))
+  if (parser.parseRegion(scopeRegion))
     return failure();
-  if (ensureRegionTerm(parser, region, regionLoc).failed())
+  if (ensureRegionTerm(parser, scopeRegion, regionLoc).failed())
     return failure();
+
+  // Parse optional cleanup region.
+  if (parser.parseOptionalKeyword("cleanup").succeeded()) {
+    if (parser.parseRegion(cleanupRegion, /*arguments=*/{}, /*argTypes=*/{}))
+      return failure();
+    if (ensureRegionTerm(parser, cleanupRegion, regionLoc).failed())
+      return failure();
+  }
+
   return success();
 }
 
 static void printOmittedTerminatorRegion(mlir::OpAsmPrinter &printer,
                                          cir::ScopeOp &op,
-                                         mlir::Region &region) {
-  printer.printRegion(region,
+                                         mlir::Region &scopeRegion,
+                                         mlir::Region &cleanupRegion) {
+  printer.printRegion(scopeRegion,
                       /*printEntryBlockArgs=*/false,
-                      /*printBlockTerminators=*/!omitRegionTerm(region));
+                      /*printBlockTerminators=*/!omitRegionTerm(scopeRegion));
+  if (!op.getCleanupRegion().empty()) {
+    printer << " cleanup ";
+    printer.printRegion(
+        cleanupRegion,
+        /*printEntryBlockArgs=*/false,
+        /*printBlockTerminators=*/!omitRegionTerm(cleanupRegion));
+  }
 }
 
 //===----------------------------------------------------------------------===//
@@ -1251,6 +1270,7 @@ void cir::ScopeOp::getSuccessorRegions(
 
   // If the condition isn't constant, both regions may be executed.
   regions.push_back(RegionSuccessor(&getScopeRegion()));
+  regions.push_back(RegionSuccessor(&getCleanupRegion()));
 }
 
 void cir::ScopeOp::build(
@@ -1261,6 +1281,8 @@ void cir::ScopeOp::build(
   OpBuilder::InsertionGuard guard(builder);
   Region *scopeRegion = result.addRegion();
   builder.createBlock(scopeRegion);
+  // cleanup region, do not eagarly create blocks, do it upon demand.
+  (void)result.addRegion();
 
   mlir::Type yieldTy;
   scopeBuilder(builder, yieldTy, result.location);
@@ -1276,17 +1298,22 @@ void cir::ScopeOp::build(
   OpBuilder::InsertionGuard guard(builder);
   Region *scopeRegion = result.addRegion();
   builder.createBlock(scopeRegion);
+  // cleanup region, do not eagarly create blocks, do it upon demand.
+  (void)result.addRegion();
   scopeBuilder(builder, result.location);
 }
 
 LogicalResult cir::ScopeOp::verify() {
-  if (getRegion().empty()) {
+  if (getScopeRegion().empty()) {
     return emitOpError() << "cir.scope must not be empty since it should "
                             "include at least an implicit cir.yield ";
   }
 
-  if (getRegion().back().empty() ||
-      !getRegion().back().getTerminator()->hasTrait<OpTrait::IsTerminator>())
+  if (getScopeRegion().back().empty() ||
+      !getScopeRegion()
+           .back()
+           .getTerminator()
+           ->hasTrait<OpTrait::IsTerminator>())
     return emitOpError() << "last block of cir.scope must be terminated";
   return success();
 }

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

@@ -141,9 +141,9 @@ class CIRScopeOpFlattening : public mlir::OpRewritePattern<cir::ScopeOp> {
       continueBlock->addArguments(scopeOp.getResultTypes(), loc);
 
     // Inline body region.
-    auto *beforeBody = &scopeOp.getRegion().front();
-    auto *afterBody = &scopeOp.getRegion().back();
-    rewriter.inlineRegionBefore(scopeOp.getRegion(), continueBlock);
+    auto *beforeBody = &scopeOp.getScopeRegion().front();
+    auto *afterBody = &scopeOp.getScopeRegion().back();
+    rewriter.inlineRegionBefore(scopeOp.getScopeRegion(), continueBlock);
 
     // Save stack and then branch into the body of the region.
     rewriter.setInsertionPointToEnd(currentBlock);

clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp

@@ -853,7 +853,7 @@ class CIRScopeOpLowering : public mlir::OpConversionPattern<cir::ScopeOp> {
       return mlir::success();
     }
 
-    for (auto &block : scopeOp.getRegion()) {
+    for (auto &block : scopeOp.getScopeRegion()) {
       rewriter.setInsertionPointToEnd(&block);
       auto *terminator = block.getTerminator();
       rewriter.replaceOpWithNewOp<mlir::memref::AllocaScopeReturnOp>(

clang/test/CIR/IR/scope.cir

@@ -4,15 +4,18 @@
 
 module {
   // Should properly print/parse scope with implicit empty yield.
+  // CHECK-LABEL: implicit_yield
   cir.func @implicit_yield() {
     cir.scope {
     }
     // CHECK: cir.scope {
-    // CHECK: }
+    // CHECK-NEXT: }
+    // CHECK-NEXT: cir.return
     cir.return
   }
 
   // Should properly print/parse scope with explicit yield.
+  // CHECK-LABEL: explicit_yield
   cir.func @explicit_yield() {
     %0 = cir.scope {
       %1 = cir.alloca !u32i, !cir.ptr<!u32i>, ["a", init] {alignment = 4 : i64}
@@ -24,4 +27,31 @@ module {
     // CHECK: } : !cir.ptr<!u32i>
     cir.return
   }
+
+  // Handle optional cleanup presence
+  // CHECK-LABEL: empty_cleanup
+  cir.func @empty_cleanup() {
+    cir.scope {
+    } cleanup {
+    }
+    // CHECK:      cir.scope {
+    // CHECK-NEXT: } cleanup {
+    // CHECK-NEXT: }
+    // CHECK-NEXT: cir.return
+    cir.return
+  }
+
+  // Handle optional cleanup presence
+  // CHECK-LABEL: some_cleanup
+  cir.func @some_cleanup() {
+    cir.scope {
+    } cleanup {
+      %1 = cir.alloca !u32i, !cir.ptr<!u32i>, ["a", init] {alignment = 4 : i64}
+    }
+    // CHECK: cir.scope {
+    // CHECK: } cleanup {
+    // CHECK:   cir.alloca
+    // CHECK: }
+    cir.return
+  }
 }