ce3485a0cd
https://godbolt.org/z/frjhqMKqc for an example. Removal of allocations due to empty `__cxa_atexit` destructor calls is done by the following globalopt pass. This pass currently does not look for `atexit` handlers generated for platforms that do not use `__cxa_atexit`. By default Win32 and AIX use `atexit`. I don't see an easy way to only remove `atexit` calls that the compiler generated without looking at the generated mangled name of the atexit handler that is being registered. However we can easily remove all `atexit` calls that register empty handlers since it is trivial to ensure the removed call still returns `0` which is the value for success.
55 lines
1.9 KiB
LLVM
55 lines
1.9 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
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; RUN: opt < %s -S -passes=globalopt | FileCheck %s
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declare dso_local i32 @atexit(ptr)
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define dso_local void @empty_atexit_handler() {
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; CHECK-LABEL: define dso_local void @empty_atexit_handler() local_unnamed_addr {
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; CHECK-NEXT: ret void
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;
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ret void
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}
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; Check that `atexit` is removed if the handler is empty.
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; Check that a removed `atexit` call returns `0` which is the value that denotes success.
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define dso_local noundef i32 @register_atexit_handler() {
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; CHECK-LABEL: define dso_local noundef i32 @register_atexit_handler() local_unnamed_addr {
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; CHECK-NEXT: ret i32 0
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;
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%1 = call i32 @atexit(ptr @empty_atexit_handler)
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ret i32 %1
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}
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declare dso_local void @declared_atexit_handler()
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; Check that an atexit handler with only a declaration is not removed.
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define dso_local noundef i32 @register_declared_atexit_handler() {
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; CHECK-LABEL: define dso_local noundef i32 @register_declared_atexit_handler() local_unnamed_addr {
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; CHECK-NEXT: [[TMP1:%.*]] = call i32 @atexit(ptr @declared_atexit_handler)
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; CHECK-NEXT: ret i32 [[TMP1]]
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;
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%1 = call i32 @atexit(ptr @declared_atexit_handler)
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ret i32 %1
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}
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declare dso_local void @external_exit_func()
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define dso_local void @nonempty_atexit_handler() {
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; CHECK-LABEL: define dso_local void @nonempty_atexit_handler() {
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; CHECK-NEXT: call void @external_exit_func()
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; CHECK-NEXT: ret void
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;
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call void @external_exit_func()
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ret void
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}
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; Check that an atexit handler that consists of any instructions other than `ret` is considered nonempty and not removed.
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define dso_local noundef i32 @register_nonempty_atexit_handler() {
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; CHECK-LABEL: define dso_local noundef i32 @register_nonempty_atexit_handler() local_unnamed_addr {
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; CHECK-NEXT: [[TMP1:%.*]] = call i32 @atexit(ptr @nonempty_atexit_handler)
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; CHECK-NEXT: ret i32 [[TMP1]]
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;
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%1 = call i32 @atexit(ptr @nonempty_atexit_handler)
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ret i32 %1
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}
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