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In GCC, the .refptr stubs are only generated for x86_64, and only for code models medium and larger (and medium is the default for x86_64 since this was introduced). They can be omitted for projects that are conscious about performance and size, and don't need automatically importing dll data members, by passing -mcmodel=small. In Clang/LLVM, such .refptr stubs are generated for any potentially symbol reference that might end up autoimported. The .refptr stubs are emitted for three separate reasons: - Without .refptr stubs, undefined symbols are mostly referenced with 32 bit wide relocations. If the symbol ends up autoimported from a different DLL, a 32 bit relative offset might not be enough to reference data in a different DLL, depending on runtime loader layout. - Without .refptr stubs, the runtime pseudo relocation mechanism will need to temporarily make sections read-write-executable if there are such relocations in the text section - On ARM and AArch64, the immediate addressing encoded into instructions isn't in the form of a plain 32 bit relative offset, but is expressed with various bits scattered throughout two instructions - the mingw runtime pseudo relocation mechanism doesn't support updating offsets in that form. If autoimporting is known not to be needed, the user can now compile with -fno-auto-import, avoiding the extra overhead of the .refptr stubs. However, omitting them is potentially fragile as the code might still rely on automatically importing some symbol without the developer knowing. If this happens, linking still usually will succeed, but users may encounter issues at runtime. Therefore, if the new option -fno-auto-import is passed to the compiler when driving linking, it passes the flag --disable-auto-import to the linker, making sure that no symbols actually are autoimported when the generated code doesn't expect it. Differential Revision: https://reviews.llvm.org/D61670
152 lines
7.8 KiB
C
152 lines
7.8 KiB
C
// RUN: %clang_cc1 -triple x86_64-pc-win32 -emit-llvm %s -o - | FileCheck --check-prefix=COFF %s
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// COFF: @baz = dso_local global i32 42
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// COFF-NEXT: @import_var = external dllimport global i32
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// COFF-NEXT: @weak_bar = extern_weak global i32
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// COFF-NEXT: @bar = external dso_local global i32
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// COFF-NEXT: @local_thread_var = dso_local thread_local global i32 42
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// COFF-NEXT: @thread_var = external dso_local thread_local global i32
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// COFF-DAG: declare dso_local void @foo()
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// COFF-DAG: define dso_local ptr @zed()
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// COFF-DAG: declare dllimport void @import_func()
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// RUN: %clang_cc1 -triple x86_64-w64-mingw32 -emit-llvm %s -o - | FileCheck --check-prefixes=MINGW,MINGW-NATIVE_TLS,MINGW-AUTO-IMPORT %s
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// RUN: %clang_cc1 -triple x86_64-w64-mingw32 -emit-llvm %s -o - -fno-auto-import | FileCheck --check-prefixes=MINGW,MINGW-NATIVE_TLS,MINGW-NO-AUTO-IMPORT %s
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// RUN: %clang_cc1 -triple x86_64-w64-mingw32 -emit-llvm %s -o - -femulated-tls | FileCheck --check-prefixes=MINGW,MINGW-EMUTLS,MINGW-AUTO-IMPORT %s
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// MINGW: @baz = dso_local global i32 42
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// MINGW-NEXT: @import_var = external dllimport global i32
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// MINGW-NEXT: @weak_bar = extern_weak global i32
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// MINGW-AUTO-IMPORT-NEXT: @bar = external global i32
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// MINGW-NO-AUTO-IMPORT-NEXT: @bar = external dso_local global i32
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// MINGW-NEXT: @local_thread_var = dso_local thread_local global i32 42
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// MINGW-NATIVE_TLS-NEXT: @thread_var = external dso_local thread_local global i32
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// MINGW-EMUTLS-NEXT: @thread_var = external thread_local global i32
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// MINGW-DAG: declare dso_local void @foo()
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// MINGW-DAG: define dso_local ptr @zed()
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// MINGW-DAG: declare dllimport void @import_func()
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/// Static relocation model defaults to -fdirect-access-external-data and sets
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/// dso_local on most global objects.
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm -mrelocation-model static %s -o - | FileCheck --check-prefix=STATIC %s
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm -mrelocation-model static -fdirect-access-external-data %s -o - | FileCheck --check-prefix=STATIC %s
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// STATIC: @baz = dso_local global i32 42
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// STATIC-NEXT: @import_var = external dso_local global i32
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// STATIC-NEXT: @weak_bar = extern_weak dso_local global i32
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// STATIC-NEXT: @bar = external dso_local global i32
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// STATIC-NEXT: @local_thread_var = dso_local thread_local global i32 42
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// STATIC-NEXT: @thread_var = external thread_local global i32
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// STATIC-DAG: declare dso_local void @foo()
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// STATIC-DAG: define dso_local ptr @zed()
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// STATIC-DAG: declare dso_local void @import_func()
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// STATIC-NOT: !"direct-access-external-data"
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/// If -fno-direct-access-external-data is set, drop dso_local from global variable
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/// declarations.
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm %s -mrelocation-model static -fno-direct-access-external-data -o - | FileCheck --check-prefix=STATIC-INDIRECT %s
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// STATIC-INDIRECT: @baz = dso_local global i32 42
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// STATIC-INDIRECT-NEXT: @import_var = external global i32
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// STATIC-INDIRECT-NEXT: @weak_bar = extern_weak global i32
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// STATIC-INDIRECT-NEXT: @bar = external global i32
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// STATIC-INDIRECT-NEXT: @local_thread_var = dso_local thread_local global i32 42
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// STATIC-INDIRECT-NEXT: @thread_var = external thread_local global i32
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// STATIC-INDIRECT-DAG: declare void @import_func()
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// STATIC-INDIRECT-DAG: define dso_local ptr @zed()
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// STATIC-INDIRECT-DAG: declare void @foo()
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// STATIC-INDIRECT: ![[#]] = !{i32 7, !"direct-access-external-data", i32 0}
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm -pic-level 1 -pic-is-pie %s -o - | FileCheck --check-prefix=PIE %s
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// PIE: @baz = dso_local global i32 42
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// PIE-NEXT: @import_var = external global i32
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// PIE-NEXT: @weak_bar = extern_weak global i32
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// PIE-NEXT: @bar = external global i32
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// PIE-NEXT: @local_thread_var = dso_local thread_local global i32 42
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// PIE-NEXT: @thread_var = external thread_local global i32
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// PIE-DAG: declare void @foo()
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// PIE-DAG: define dso_local ptr @zed()
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// PIE-DAG: declare void @import_func()
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// PIE-NOT: !"direct-access-external-data"
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm -pic-level 1 -pic-is-pie -fdirect-access-external-data %s -o - | FileCheck --check-prefix=PIE-DIRECT %s
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// PIE-DIRECT: @baz = dso_local global i32 42
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// PIE-DIRECT-NEXT: @import_var = external dso_local global i32
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// PIE-DIRECT-NEXT: @weak_bar = extern_weak global i32
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// PIE-DIRECT-NEXT: @bar = external dso_local global i32
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// PIE-DIRECT-NEXT: @local_thread_var = dso_local thread_local global i32 42
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// PIE-DIRECT-NEXT: @thread_var = external thread_local global i32
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// PIE-DIRECT-DAG: declare void @foo()
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// PIE-DIRECT-DAG: define dso_local ptr @zed()
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// PIE-DIRECT-DAG: declare void @import_func()
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// PIE-DIRECT: ![[#]] = !{i32 7, !"direct-access-external-data", i32 1}
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm -mrelocation-model static -fno-plt %s -o - | FileCheck --check-prefix=NOPLT %s
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// NOPLT: @baz = dso_local global i32 42
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// NOPLT-NEXT: @import_var = external dso_local global i32
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// NOPLT-NEXT: @weak_bar = extern_weak dso_local global i32
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// NOPLT-NEXT: @bar = external dso_local global i32
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// NOPLT-NEXT: @local_thread_var = dso_local thread_local global i32 42
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// NOPLT-NEXT: @thread_var = external thread_local global i32
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// NOPLT-DAG: declare void @foo()
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// NOPLT-DAG: define dso_local ptr @zed()
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// NOPLT-DAG: declare void @import_func()
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm -fno-plt -pic-level 1 -pic-is-pie -fdirect-access-external-data %s -o - | FileCheck --check-prefix=PIE-DIRECT-NOPLT %s
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// PIE-DIRECT-NOPLT: @baz = dso_local global i32 42
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// PIE-DIRECT-NOPLT-NEXT: @import_var = external dso_local global i32
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// PIE-DIRECT-NOPLT-NEXT: @weak_bar = extern_weak global i32
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// PIE-DIRECT-NOPLT-NEXT: @bar = external dso_local global i32
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// PIE-DIRECT-NOPLT-NEXT: @local_thread_var = dso_local thread_local global i32 42
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// PIE-DIRECT-NOPLT-NEXT: @thread_var = external thread_local global i32
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// PIE-DIRECT-NOPLT-DAG: declare void @foo()
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// PIE-DIRECT-NOPLT-DAG: define dso_local ptr @zed()
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// PIE-DIRECT-NOPLT-DAG: declare void @import_func()
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm -pic-level 1 -pic-is-pie -fno-plt %s -o - | FileCheck --check-prefix=PIE-NO-PLT %s
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// RUN: %clang_cc1 -triple powerpc64le -emit-llvm -mrelocation-model static %s -o - | FileCheck --check-prefix=PIE-NO-PLT %s
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// PIE-NO-PLT: @baz = dso_local global i32 42
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// PIE-NO-PLT-NEXT: @import_var = external global i32
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// PIE-NO-PLT-NEXT: @weak_bar = extern_weak global i32
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// PIE-NO-PLT-NEXT: @bar = external global i32
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// PIE-NO-PLT-NEXT: @local_thread_var = dso_local thread_local global i32 42
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// PIE-NO-PLT-NEXT: @thread_var = external thread_local global i32
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// PIE-NO-PLT-DAG: declare void @import_func()
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// PIE-NO-PLT-DAG: define dso_local ptr @zed()
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// PIE-NO-PLT-DAG: declare void @foo()
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/// -fdirect-access-external-data is currently ignored for -fPIC.
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm -pic-level 2 %s -o - | FileCheck --check-prefix=SHARED %s
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// RUN: %clang_cc1 -triple x86_64 -emit-llvm -pic-level 2 -fdirect-access-external-data %s -o - | FileCheck --check-prefix=SHARED %s
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// SHARED-DAG: @bar = external global i32
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// SHARED-DAG: @weak_bar = extern_weak global i32
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// SHARED-DAG: declare void @foo()
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// SHARED-DAG: @baz ={{.*}} global i32 42
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// SHARED-DAG: define{{.*}} ptr @zed()
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// SHARED-DAG: @thread_var = external thread_local global i32
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// SHARED-DAG: @local_thread_var ={{.*}} thread_local global i32 42
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int baz = 42;
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__attribute__((dllimport)) extern int import_var;
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__attribute__((weak)) extern int weak_bar;
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extern int bar;
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__attribute__((dllimport)) void import_func(void);
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int *use_import(void) {
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import_func();
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return &import_var;
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}
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void foo(void);
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int *zed(void) {
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foo();
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return baz ? &weak_bar : &bar;
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}
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__thread int local_thread_var = 42;
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extern __thread int thread_var;
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int *get_thread_var(int a) {
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return a ? &thread_var : &local_thread_var;
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}
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