[clang] [CIR] Implement Statement Expressions (PR #153677)

[Bruno Cardoso Lopes via cfe-commits]

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@@ -23,16 +25,57 @@ using namespace clang;
 using namespace clang::CIRGen;
 using namespace cir;
 
-void CIRGenFunction::emitCompoundStmtWithoutScope(const CompoundStmt &s) {
-  for (auto *curStmt : s.body()) {
-    if (emitStmt(curStmt, /*useCurrentScope=*/false).failed())
-      getCIRGenModule().errorNYI(curStmt->getSourceRange(),
-                                 std::string("emitCompoundStmtWithoutScope: ") +
-                                     curStmt->getStmtClassName());
+mlir::LogicalResult CIRGenFunction::emitCompoundStmtWithoutScope(
+    const CompoundStmt &s, Address *lastValue, AggValueSlot slot) {
+  mlir::LogicalResult result = mlir::success();
+  const Stmt *exprResult = s.getStmtExprResult();
+  assert((!lastValue || (lastValue && exprResult)) &&
+         "If lastValue is not null then the CompoundStmt must have a "
+         "StmtExprResult");
+
+  for (const Stmt *curStmt : s.body()) {
+    // We have to special case labels here. They are statements, but when put
+    // at the end of a statement expression, they yield the value of their
+    // subexpression. Handle this by walking through all labels we encounter,
+    // emitting them before we evaluate the subexpr.
+    // Similar issues arise for attributed statements.
+    if (lastValue && exprResult == curStmt) {
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bcardosolopes wrote:

Might be cleaner to factor the content of this `if` out in a helper function.

https://github.com/llvm/llvm-project/pull/153677