[CIR] Implement init priority attribute (#1907)

Fixes #1743.

Author: badumbatish

clang/include/clang/CIR/Interfaces/ASTAttrInterfaces.td

@@ -28,6 +28,13 @@ let cppNamespace = "::cir" in {
         /*defaultImplementation=*/ [{
           return $_attr.getAst()->template hasAttr<clang::InitPriorityAttr>();
         }]
+      >,
+
+      // Requires hasInitPriorityAttr before dereferencing
+      InterfaceMethod<"", "const clang::InitPriorityAttr*", "getInitPriorityAttr", (ins), [{}],
+        /*defaultImplementation=*/ [{
+          return $_attr.getAst()->template getAttr<clang::InitPriorityAttr>();
+        }]
       >
     ];
   }

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

@@ -905,10 +905,9 @@ void LoweringPreparePass::lowerGlobalOp(GlobalOp op) {
     ctorRegion.getBlocks().clear();
     dtorRegion.getBlocks().clear();
 
-    // Add a function call to the variable initialization function.
-    assert(!hasAttr<clang::InitPriorityAttr>(
-               mlir::cast<ASTDeclInterface>(*op.getAst())) &&
-           "custom initialization priority NYI");
+    auto astDecl = mlir::cast<ASTDeclInterface>(*op.getAst());
+    if (astDecl.hasInitPriorityAttr())
+      f.setGlobalCtorPriority(astDecl.getInitPriorityAttr()->getPriority());
     dynamicInitializers.push_back(f);
   }
 
@@ -955,8 +954,9 @@ void LoweringPreparePass::buildCXXGlobalInitFunc() {
   for (auto &f : dynamicInitializers) {
     // TODO: handle globals with a user-specified initialzation priority.
     // TODO: handle defaule priority more nicely.
-    globalCtorList.emplace_back(f.getName(),
-                                cir::DefaultGlobalCtorDtorPriority);
+    globalCtorList.emplace_back(
+        f.getName(),
+        f.getGlobalCtorPriority().value_or(cir::DefaultGlobalCtorDtorPriority));
   }
 
   SmallString<256> fnName;

clang/test/CIR/CodeGen/init_priority.cpp

@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s -check-prefix=CIR
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s -check-prefix=LLVM
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-llvm %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s -check-prefix=OGCG
+
+// CIR: attributes {cir.global_ctors = [#cir.global_ctor<"__cxx_global_var_init", 101>]
+// LLVM: @llvm.global_ctors = appending constant{{.*}}{ i32 101, ptr @__cxx_global_var_init, ptr null }
+// OGCG: @llvm.global_ctors = appending global{{.*}}{ i32 101, ptr @_GLOBAL__I_000101, ptr null }
+class A {
+public:
+  A(int, int);
+} A __attribute((init_priority(101)))(0, 0);
+
+// CIR-LABEL: cir.func internal private @__cxx_global_var_init() global_ctor(101)  {
+// LLVM-LABEL: define internal void @__cxx_global_var_init() {
+// OGCG-LABEL: define internal void @_GLOBAL__I_000101() {{.*}} section ".text.startup" {