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[CIR] Fix a problem with global array dtor lowering (#169416)
In the LoweringPrepare pass, the handling for global array destructor lowering was mishandling the insertion point, so that if this code needed to create a declaration for the __cxa_atexit function, that declaration was being created in the dtor region, rather than at module scope. This change fixes that.
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‎clang/lib/CIR/Dialect/Transforms/LoweringPrepare.cpp‎

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@@ -702,6 +702,7 @@ cir::FuncOp LoweringPreparePass::getOrCreateDtorFunc(CIRBaseBuilderTy &builder,
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cir::GlobalOp op,
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mlir::Region &dtorRegion,
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cir::CallOp &dtorCall) {
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mlir::OpBuilder::InsertionGuard guard(builder);
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assert(!cir::MissingFeatures::astVarDeclInterface());
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assert(!cir::MissingFeatures::opGlobalThreadLocal());
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‎clang/test/CIR/CodeGen/global-array-dtor.cpp‎

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// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir -mmlir --mlir-print-ir-before=cir-lowering-prepare %s -o %t.cir 2> %t-before.cir
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// RUN: FileCheck --input-file=%t-before.cir %s --check-prefix=CIR-BEFORE-LPP
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// RUN: FileCheck --input-file=%t.cir %s --check-prefix=CIR
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// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o %t-cir.ll
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// RUN: FileCheck --input-file=%t-cir.ll %s --check-prefix=LLVM
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// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -emit-llvm %s -o %t.ll
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// RUN: FileCheck --input-file=%t.ll %s --check-prefix=OGCG
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// This duplicates a test case in global-init.cpp, but having it by itself
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// forces the __cxa_atexit function to be emitted for this case, which was
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// broken in the original implementation.
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struct ArrayDtor {
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~ArrayDtor();
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};
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ArrayDtor arrDtor[16];
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// CIR-BEFORE-LPP: cir.global external @arrDtor = #cir.zero : !cir.array<!rec_ArrayDtor x 16>
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// CIR-BEFORE-LPP-SAME: dtor {
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// CIR-BEFORE-LPP: %[[THIS:.*]] = cir.get_global @arrDtor : !cir.ptr<!cir.array<!rec_ArrayDtor x 16>>
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// CIR-BEFORE-LPP: cir.array.dtor %[[THIS]] : !cir.ptr<!cir.array<!rec_ArrayDtor x 16>> {
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// CIR-BEFORE-LPP: ^bb0(%[[ELEM:.*]]: !cir.ptr<!rec_ArrayDtor>):
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// CIR-BEFORE-LPP: cir.call @_ZN9ArrayDtorD1Ev(%[[ELEM]]) nothrow : (!cir.ptr<!rec_ArrayDtor>) -> ()
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// CIR-BEFORE-LPP: cir.yield
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// CIR-BEFORE-LPP: }
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// CIR-BEFORE-LPP: }
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// CIR: cir.global external @arrDtor = #cir.zero : !cir.array<!rec_ArrayDtor x 16> {alignment = 16 : i64}
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// CIR: cir.func internal private @__cxx_global_array_dtor(%[[ARR_ARG:.*]]: !cir.ptr<!void> {{.*}}) {
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// CIR: %[[CONST15:.*]] = cir.const #cir.int<15> : !u64i
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// CIR: %[[BEGIN:.*]] = cir.cast array_to_ptrdecay %[[ARR_ARG]] : !cir.ptr<!void> -> !cir.ptr<!rec_ArrayDtor>
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// CIR: %[[END:.*]] = cir.ptr_stride %[[BEGIN]], %[[CONST15]] : (!cir.ptr<!rec_ArrayDtor>, !u64i) -> !cir.ptr<!rec_ArrayDtor>
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// CIR: %[[CUR_ADDR:.*]] = cir.alloca !cir.ptr<!rec_ArrayDtor>, !cir.ptr<!cir.ptr<!rec_ArrayDtor>>, ["__array_idx"]
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// CIR: cir.store %[[END]], %[[CUR_ADDR]] : !cir.ptr<!rec_ArrayDtor>, !cir.ptr<!cir.ptr<!rec_ArrayDtor>>
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// CIR: cir.do {
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// CIR: %[[CUR:.*]] = cir.load %[[CUR_ADDR]] : !cir.ptr<!cir.ptr<!rec_ArrayDtor>>, !cir.ptr<!rec_ArrayDtor>
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// CIR: cir.call @_ZN9ArrayDtorD1Ev(%[[CUR]]) nothrow : (!cir.ptr<!rec_ArrayDtor>) -> ()
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// CIR: %[[NEG_ONE:.*]] = cir.const #cir.int<-1> : !s64i
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// CIR: %[[NEXT:.*]] = cir.ptr_stride %[[CUR]], %[[NEG_ONE]] : (!cir.ptr<!rec_ArrayDtor>, !s64i) -> !cir.ptr<!rec_ArrayDtor>
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// CIR: cir.store %[[NEXT]], %[[CUR_ADDR]] : !cir.ptr<!rec_ArrayDtor>, !cir.ptr<!cir.ptr<!rec_ArrayDtor>>
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// CIR: cir.yield
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// CIR: } while {
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// CIR: %[[CUR:.*]] = cir.load %[[CUR_ADDR]] : !cir.ptr<!cir.ptr<!rec_ArrayDtor>>, !cir.ptr<!rec_ArrayDtor>
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// CIR: %[[CMP:.*]] = cir.cmp(ne, %[[CUR]], %[[BEGIN]]) : !cir.ptr<!rec_ArrayDtor>, !cir.bool
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// CIR: cir.condition(%[[CMP]])
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// CIR: }
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// CIR: cir.return
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// CIR: }
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//
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// CIR: cir.func internal private @__cxx_global_var_init() {
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// CIR: %[[ARR:.*]] = cir.get_global @arrDtor : !cir.ptr<!cir.array<!rec_ArrayDtor x 16>>
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// CIR: %[[DTOR:.*]] = cir.get_global @__cxx_global_array_dtor : !cir.ptr<!cir.func<(!cir.ptr<!void>)>>
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// CIR: %[[DTOR_CAST:.*]] = cir.cast bitcast %[[DTOR]] : !cir.ptr<!cir.func<(!cir.ptr<!void>)>> -> !cir.ptr<!cir.func<(!cir.ptr<!void>)>>
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// CIR: %[[ARR_CAST:.*]] = cir.cast bitcast %[[ARR]] : !cir.ptr<!cir.array<!rec_ArrayDtor x 16>> -> !cir.ptr<!void>
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// CIR: %[[HANDLE:.*]] = cir.get_global @__dso_handle : !cir.ptr<i8>
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// CIR: cir.call @__cxa_atexit(%[[DTOR_CAST]], %[[ARR_CAST]], %[[HANDLE]]) : (!cir.ptr<!cir.func<(!cir.ptr<!void>)>>, !cir.ptr<!void>, !cir.ptr<i8>) -> ()
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// LLVM: define internal void @__cxx_global_array_dtor(ptr %[[ARR_ARG:.*]]) {
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// LLVM: %[[BEGIN:.*]] = getelementptr %struct.ArrayDtor, ptr %[[ARR_ARG]], i32 0
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// LLVM: %[[END:.*]] = getelementptr %struct.ArrayDtor, ptr %[[BEGIN]], i64 15
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// LLVM: %[[CUR_ADDR:.*]] = alloca ptr
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// LLVM: store ptr %[[END]], ptr %[[CUR_ADDR]]
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// LLVM: br label %[[LOOP_BODY:.*]]
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// LLVM: [[LOOP_COND:.*]]:
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// LLVM: %[[CUR:.*]] = load ptr, ptr %[[CUR_ADDR]]
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// LLVM: %[[CMP:.*]] = icmp ne ptr %[[CUR]], %[[BEGIN]]
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// LLVM: br i1 %[[CMP]], label %[[LOOP_BODY]], label %[[LOOP_END:.*]]
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// LLVM: [[LOOP_BODY]]:
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// LLVM: %[[CUR:.*]] = load ptr, ptr %[[CUR_ADDR]]
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// LLVM: call void @_ZN9ArrayDtorD1Ev(ptr %[[CUR]]) #0
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// LLVM: %[[PREV:.*]] = getelementptr %struct.ArrayDtor, ptr %[[CUR]], i64 -1
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// LLVM: store ptr %[[PREV]], ptr %[[CUR_ADDR]]
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// LLVM: br label %[[LOOP_COND]]
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// LLVM: [[LOOP_END]]:
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// LLVM: ret void
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// LLVM: }
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//
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// LLVM: define internal void @__cxx_global_var_init() {
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// LLVM: call void @__cxa_atexit(ptr @__cxx_global_array_dtor, ptr @arrDtor, ptr @__dso_handle)
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// Note: OGCG defines these functions in reverse order of CIR->LLVM.
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// Note also: OGCG doesn't pass the address of the array to the destructor function.
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// Instead, it uses the global directly in the helper function.
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// OGCG: define internal void @__cxx_global_var_init() {{.*}} section ".text.startup" {
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// OGCG: call i32 @__cxa_atexit(ptr @__cxx_global_array_dtor, ptr null, ptr @__dso_handle)
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// OGCG: define internal void @__cxx_global_array_dtor(ptr noundef %[[ARG:.*]]) {{.*}} section ".text.startup" {
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// OGCG: entry:
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// OGCG: %[[UNUSED_ADDR:.*]] = alloca ptr
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// OGCG: store ptr %[[ARG]], ptr %[[UNUSED_ADDR]]
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// OGCG: br label %[[LOOP_BODY:.*]]
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// OGCG: [[LOOP_BODY]]:
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// OGCG: %[[PREV:.*]] = phi ptr [ getelementptr inbounds (%struct.ArrayDtor, ptr @arrDtor, i64 16), %entry ], [ %[[CUR:.*]], %[[LOOP_BODY]] ]
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// OGCG: %[[CUR]] = getelementptr inbounds %struct.ArrayDtor, ptr %[[PREV]], i64 -1
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// OGCG: call void @_ZN9ArrayDtorD1Ev(ptr noundef nonnull align 1 dereferenceable(1) %[[CUR]])
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// OGCG: %[[DONE:.*]] = icmp eq ptr %[[CUR]], @arrDtor
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// OGCG: br i1 %[[DONE]], label %[[LOOP_END:.*]], label %[[LOOP_BODY]]
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// OGCG: [[LOOP_END]]:
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// OGCG: ret void
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// OGCG: }
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// Common init function for all globals with default priority
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// CIR: cir.func private @_GLOBAL__sub_I_[[FILENAME:.*]]() {
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// CIR: cir.call @__cxx_global_var_init() : () -> ()
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// LLVM: define void @_GLOBAL__sub_I_[[FILENAME:.*]]()
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// LLVM: call void @__cxx_global_var_init()
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// OGCG: define internal void @_GLOBAL__sub_I_[[FILENAME:.*]]() {{.*}} section ".text.startup" {
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// OGCG: call void @__cxx_global_var_init()

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