[CIR][CIRGen] Fix some alias issues under -O1 and above

Note that there are still missing pieces, which will be incrementally
addressed.

Author: bcardosolopes

clang/lib/CIR/CodeGen/CIRGenCXX.cpp

@@ -174,7 +174,7 @@ bool CIRGenModule::tryEmitBaseDestructorAsAlias(const CXXDestructorDecl *D) {
     llvm_unreachable("NYI");
 
   // Create the alias with no name.
-  buildAliasForGlobal("", Entry, AliasDecl, Aliasee, Linkage);
+  buildAliasForGlobal(MangledName, Entry, AliasDecl, Aliasee, Linkage);
   return false;
 }
 

clang/lib/CIR/CodeGen/CIRGenModule.cpp

@@ -2139,9 +2139,15 @@ void CIRGenModule::buildAliasForGlobal(StringRef mangledName,
                                        mlir::cir::GlobalLinkageKind linkage) {
   auto *aliasFD = dyn_cast<FunctionDecl>(aliasGD.getDecl());
   assert(aliasFD && "expected FunctionDecl");
-  auto alias =
-      createCIRFunction(getLoc(aliasGD.getDecl()->getSourceRange()),
-                        mangledName, aliasee.getFunctionType(), aliasFD);
+
+  // The aliasee function type is different from the alias one, this difference
+  // is specific to CIR because in LLVM the ptr types are already erased at this
+  // point.
+  auto &fnInfo = getTypes().arrangeCXXStructorDeclaration(aliasGD);
+  auto fnType = getTypes().GetFunctionType(fnInfo);
+
+  auto alias = createCIRFunction(getLoc(aliasGD.getDecl()->getSourceRange()),
+                                 mangledName, fnType, aliasFD);
   alias.setAliasee(aliasee.getName());
   alias.setLinkage(linkage);
   // Declarations cannot have public MLIR visibility, just mark them private

clang/test/CIR/CodeGen/virtual-destructor-calls.cpp

@@ -1,6 +1,8 @@
 
 // RUN: %clang_cc1 -triple aarch64-none-linux-android21 -std=c++20 -mconstructor-aliases -O0 -fclangir -emit-cir %s -o %t.cir
 // RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
+// RUN: %clang_cc1 -triple aarch64-none-linux-android21 -std=c++20 -mconstructor-aliases -O1 -fclangir -emit-cir %s -o %t-o1.cir
+// RUN: FileCheck --check-prefix=CIR_O1 --input-file=%t-o1.cir %s
 // RUN: %clang_cc1 -triple aarch64-none-linux-android21 -std=c++20 -mconstructor-aliases -O0 -fclangir -emit-llvm -fno-clangir-call-conv-lowering %s -o %t.ll
 // RUN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s
 
@@ -38,8 +40,11 @@ struct B : A {
 // LLVM: call void @_ZdlPv
 
 // (aliases from C)
-// FIXME: this should be an alias declaration.
+// FIXME: this should be an alias declaration even in -O0
 // CIR: cir.func @_ZN1CD2Ev(%arg0: !cir.ptr<!ty_C>{{.*}})) {{.*}} {
+// CIR_O1-NOT: cir.func @_ZN1CD2Ev(%arg0: !cir.ptr<!ty_C>{{.*}})) {{.*}} {
+// CIR_O1: cir.func private @_ZN1CD2Ev(!cir.ptr<!ty_C>) alias(@_ZN1BD2Ev)
+
 // CIR: cir.func private @_ZN1CD1Ev(!cir.ptr<!ty_C>) alias(@_ZN1CD2Ev)
 
 // FIXME: LLVM output should be: @_ZN1CD2Ev ={{.*}} unnamed_addr alias {{.*}} @_ZN1BD2Ev