[CIR] Fix warnings related to unused variables in release builds (#151412)

This fixes a number of warnings in release builds due to variables that
were only being used in asserts. Some of these variables will later be
used in non-debug code, but for now they are unused in release builds.

Author: andykaylor

clang/lib/CIR/CodeGen/CIRGenCall.h

@@ -137,7 +137,7 @@ struct CallArg {
 
   /// A data-flow flag to make sure getRValue and/or copyInto are not
   /// called twice for duplicated IR emission.
-  mutable bool isUsed;
+  [[maybe_unused]] mutable bool isUsed;
 
 public:
   clang::QualType ty;

clang/lib/CIR/CodeGen/CIRGenExpr.cpp

@@ -1481,9 +1481,10 @@ Address CIRGenFunction::emitArrayToPointerDecay(const Expr *e) {
   if (e->getType()->isVariableArrayType())
     return addr;
 
-  auto pointeeTy = mlir::cast<cir::ArrayType>(lvalueAddrTy.getPointee());
+  [[maybe_unused]] auto pointeeTy =
+      mlir::cast<cir::ArrayType>(lvalueAddrTy.getPointee());
 
-  mlir::Type arrayTy = convertType(e->getType());
+  [[maybe_unused]] mlir::Type arrayTy = convertType(e->getType());
   assert(mlir::isa<cir::ArrayType>(arrayTy) && "expected array");
   assert(pointeeTy == arrayTy);
 

clang/lib/CIR/CodeGen/CIRGenExprComplex.cpp

@@ -156,12 +156,15 @@ class ComplexExprEmitter : public StmtVisitor<ComplexExprEmitter, mlir::Value> {
 };
 } // namespace
 
+#ifndef NDEBUG
+// Only used in asserts
 static const ComplexType *getComplexType(QualType type) {
   type = type.getCanonicalType();
   if (const ComplexType *comp = dyn_cast<ComplexType>(type))
     return comp;
   return cast<ComplexType>(cast<AtomicType>(type)->getValueType());
 }
+#endif // NDEBUG
 
 LValue ComplexExprEmitter::emitBinAssignLValue(const BinaryOperator *e,
                                                mlir::Value &value) {

clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp

@@ -439,7 +439,7 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
       value = builder.getTrue(cgf.getLoc(e->getExprLoc()));
     } else if (type->isIntegerType()) {
       QualType promotedType;
-      bool canPerformLossyDemotionCheck = false;
+      [[maybe_unused]] bool canPerformLossyDemotionCheck = false;
       if (cgf.getContext().isPromotableIntegerType(type)) {
         promotedType = cgf.getContext().getPromotedIntegerType(type);
         assert(promotedType != type && "Shouldn't promote to the same type.");

clang/lib/CIR/CodeGen/CIRGenFunction.cpp

@@ -216,8 +216,7 @@ void CIRGenFunction::emitAndUpdateRetAlloca(QualType type, mlir::Location loc,
 void CIRGenFunction::declare(mlir::Value addrVal, const Decl *var, QualType ty,
                              mlir::Location loc, CharUnits alignment,
                              bool isParam) {
-  const auto *namedVar = dyn_cast_or_null<NamedDecl>(var);
-  assert(namedVar && "Needs a named decl");
+  assert(isa<NamedDecl>(var) && "Needs a named decl");
   assert(!cir::MissingFeatures::cgfSymbolTable());
 
   auto allocaOp = cast<cir::AllocaOp>(addrVal.getDefiningOp());

clang/lib/CIR/CodeGen/CIRGenModule.cpp

@@ -656,8 +656,6 @@ mlir::Value CIRGenModule::getAddrOfGlobalVar(const VarDecl *d, mlir::Type ty,
 
 void CIRGenModule::emitGlobalVarDefinition(const clang::VarDecl *vd,
                                            bool isTentative) {
-  const QualType astTy = vd->getType();
-
   if (getLangOpts().OpenCL || getLangOpts().OpenMPIsTargetDevice) {
     errorNYI(vd->getSourceRange(), "emit OpenCL/OpenMP global variable");
     return;
@@ -701,7 +699,7 @@ void CIRGenModule::emitGlobalVarDefinition(const clang::VarDecl *vd,
     // never attempt to emit a tentative definition if a real one
     // exists. A use may still exists, however, so we still may need
     // to do a RAUW.
-    assert(!astTy->isIncompleteType() && "Unexpected incomplete type");
+    assert(!vd->getType()->isIncompleteType() && "Unexpected incomplete type");
     init = builder.getZeroInitAttr(convertType(vd->getType()));
   } else {
     emitter.emplace(*this);

clang/lib/CIR/CodeGen/CIRGenStmt.cpp

@@ -79,14 +79,15 @@ mlir::LogicalResult CIRGenFunction::emitStmt(const Stmt *s,
 #define EXPR(Type, Base) case Stmt::Type##Class:
 #include "clang/AST/StmtNodes.inc"
     {
-      // Remember the block we came in on.
-      mlir::Block *incoming = builder.getInsertionBlock();
-      assert(incoming && "expression emission must have an insertion point");
+      assert(builder.getInsertionBlock() &&
+             "expression emission must have an insertion point");
 
       emitIgnoredExpr(cast<Expr>(s));
 
-      mlir::Block *outgoing = builder.getInsertionBlock();
-      assert(outgoing && "expression emission cleared block!");
+      // Classic codegen has a check here to see if the emitter created a new
+      // block that isn't used (comparing the incoming and outgoing insertion
+      // points) and deletes the outgoing block if it's not used. In CIR, we
+      // will handle that during the cir.canonicalize pass.
       return mlir::success();
     }
   case Stmt::IfStmtClass: