[CIR] Upstream support for switch statements case kinds (#138003)

This introduces support for the following cir::case kinds:
- `Equal`
- `AnyOf`
- `Range`

Author: Andres-Salamanca

clang/include/clang/CIR/MissingFeatures.h

@@ -111,6 +111,10 @@ struct MissingFeatures {
   // Unary operator handling
   static bool opUnaryPromotionType() { return false; }
 
+  // SwitchOp handling
+  static bool foldCascadingCases() { return false; }
+  static bool foldRangeCase() { return false; }
+
   // Clang early optimizations or things defered to LLVM lowering.
   static bool mayHaveIntegerOverflow() { return false; }
   static bool shouldReverseUnaryCondOnBoolExpr() { return false; }
@@ -176,7 +180,6 @@ struct MissingFeatures {
   static bool targetSpecificCXXABI() { return false; }
   static bool moduleNameHash() { return false; }
   static bool setDSOLocal() { return false; }
-  static bool foldCaseStmt() { return false; }
   static bool constantFoldSwitchStatement() { return false; }
   static bool cudaSupport() { return false; }
   static bool maybeHandleStaticInExternC() { return false; }

clang/lib/CIR/CodeGen/CIRGenFunction.h

@@ -581,6 +581,10 @@ class CIRGenFunction : public CIRGenTypeCache {
   mlir::LogicalResult emitDeclStmt(const clang::DeclStmt &s);
   LValue emitDeclRefLValue(const clang::DeclRefExpr *e);
 
+  mlir::LogicalResult emitDefaultStmt(const clang::DefaultStmt &s,
+                                      mlir::Type condType,
+                                      bool buildingTopLevelCase);
+
   /// Emit an `if` on a boolean condition to the specified blocks.
   /// FIXME: Based on the condition, this might try to simplify the codegen of
   /// the conditional based on the branch.

clang/lib/CIR/CodeGen/CIRGenStmt.cpp

@@ -254,6 +254,7 @@ mlir::LogicalResult CIRGenFunction::emitSimpleStmt(const Stmt *s,
   case Stmt::NullStmtClass:
     break;
   case Stmt::CaseStmtClass:
+  case Stmt::DefaultStmtClass:
     // If we reached here, we must not handling a switch case in the top level.
     return emitSwitchCase(cast<SwitchCase>(*s),
                           /*buildingTopLevelCase=*/false);
@@ -458,7 +459,7 @@ CIRGenFunction::emitCaseDefaultCascade(const T *stmt, mlir::Type condType,
     if (isa<DefaultStmt>(sub) && isa<CaseStmt>(stmt)) {
       subStmtKind = SubStmtKind::Default;
       builder.createYield(loc);
-    } else if (isa<CaseStmt>(sub) && isa<DefaultStmt>(stmt)) {
+    } else if (isa<CaseStmt>(sub) && isa<DefaultStmt, CaseStmt>(stmt)) {
       subStmtKind = SubStmtKind::Case;
       builder.createYield(loc);
     } else {
@@ -503,8 +504,8 @@ CIRGenFunction::emitCaseDefaultCascade(const T *stmt, mlir::Type condType,
   if (subStmtKind == SubStmtKind::Case) {
     result = emitCaseStmt(*cast<CaseStmt>(sub), condType, buildingTopLevelCase);
   } else if (subStmtKind == SubStmtKind::Default) {
-    getCIRGenModule().errorNYI(sub->getSourceRange(), "Default case");
-    return mlir::failure();
+    result = emitDefaultStmt(*cast<DefaultStmt>(sub), condType,
+                             buildingTopLevelCase);
   } else if (buildingTopLevelCase) {
     // If we're building a top level case, try to restore the insert point to
     // the case we're building, then we can attach more random stmts to the
@@ -518,19 +519,40 @@ CIRGenFunction::emitCaseDefaultCascade(const T *stmt, mlir::Type condType,
 mlir::LogicalResult CIRGenFunction::emitCaseStmt(const CaseStmt &s,
                                                  mlir::Type condType,
                                                  bool buildingTopLevelCase) {
+  cir::CaseOpKind kind;
+  mlir::ArrayAttr value;
   llvm::APSInt intVal = s.getLHS()->EvaluateKnownConstInt(getContext());
-  SmallVector<mlir::Attribute, 1> caseEltValueListAttr;
-  caseEltValueListAttr.push_back(cir::IntAttr::get(condType, intVal));
-  mlir::ArrayAttr value = builder.getArrayAttr(caseEltValueListAttr);
-  if (s.getRHS()) {
-    getCIRGenModule().errorNYI(s.getSourceRange(), "SwitchOp range kind");
-    return mlir::failure();
+
+  // If the case statement has an RHS value, it is representing a GNU
+  // case range statement, where LHS is the beginning of the range
+  // and RHS is the end of the range.
+  if (const Expr *rhs = s.getRHS()) {
+    llvm::APSInt endVal = rhs->EvaluateKnownConstInt(getContext());
+    value = builder.getArrayAttr({cir::IntAttr::get(condType, intVal),
+                                  cir::IntAttr::get(condType, endVal)});
+    kind = cir::CaseOpKind::Range;
+
+    // We don't currently fold case range statements with other case statements.
+    // TODO(cir): Add this capability. Folding these cases is going to be
+    // implemented in CIRSimplify when it is upstreamed.
+    assert(!cir::MissingFeatures::foldRangeCase());
+    assert(!cir::MissingFeatures::foldCascadingCases());
+  } else {
+    value = builder.getArrayAttr({cir::IntAttr::get(condType, intVal)});
+    kind = cir::CaseOpKind::Equal;
   }
-  assert(!cir::MissingFeatures::foldCaseStmt());
-  return emitCaseDefaultCascade(&s, condType, value, cir::CaseOpKind::Equal,
+
+  return emitCaseDefaultCascade(&s, condType, value, kind,
                                 buildingTopLevelCase);
 }
 
+mlir::LogicalResult CIRGenFunction::emitDefaultStmt(const clang::DefaultStmt &s,
+                                                    mlir::Type condType,
+                                                    bool buildingTopLevelCase) {
+  return emitCaseDefaultCascade(&s, condType, builder.getArrayAttr({}),
+                                cir::CaseOpKind::Default, buildingTopLevelCase);
+}
+
 mlir::LogicalResult CIRGenFunction::emitSwitchCase(const SwitchCase &s,
                                                    bool buildingTopLevelCase) {
   assert(!condTypeStack.empty() &&
@@ -540,10 +562,9 @@ mlir::LogicalResult CIRGenFunction::emitSwitchCase(const SwitchCase &s,
     return emitCaseStmt(cast<CaseStmt>(s), condTypeStack.back(),
                         buildingTopLevelCase);
 
-  if (s.getStmtClass() == Stmt::DefaultStmtClass) {
-    getCIRGenModule().errorNYI(s.getSourceRange(), "Default case");
-    return mlir::failure();
-  }
+  if (s.getStmtClass() == Stmt::DefaultStmtClass)
+    return emitDefaultStmt(cast<DefaultStmt>(s), condTypeStack.back(),
+                           buildingTopLevelCase);
 
   llvm_unreachable("expect case or default stmt");
 }