[modules] Fix handling of initializers for templated global variables.

For global variables with unordered initialization that are instantiated
within a module, we previously did not emit the global (or its
initializer) at all unless it was used in the importing translation unit
(and sometimes not even then!), leading to misbehavior and link errors.

We now emit the initializer for an instantiated global variable with
unordered initialization with side-effects in a module into every
translation unit that imports the module. This is unfortunate, but
mostly matches the behavior of a non-modular compilation and seems to be
the best that we can reasonably do.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@353240 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 242 insertions, 0 deletions

diff --git a/test/Modules/initializers.cpp b/test/Modules/initializers.cpp
new file mode 100644
index 0000000000..bba016c237
--- /dev/null
+++ b/test/Modules/initializers.cpp
@@ -0,0 +1,242 @@
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -std=c++17 -emit-llvm -DIMPORT=1 -fmodules %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-IMPORT,CHECK-NO-NS,CHECK-IMPORT-NO-NS --implicit-check-not=unused
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -std=c++17 -emit-llvm -DIMPORT=1 -DNS -fmodules %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-IMPORT,CHECK-NS,CHECK-IMPORT-NS --implicit-check-not=unused
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -std=c++17 -emit-llvm -DIMPORT=2 -fmodules %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-NO-NS --implicit-check-not=unused
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -std=c++17 -emit-llvm -DIMPORT=2 -DNS -fmodules %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-NS --implicit-check-not=unused
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -std=c++17 -emit-llvm -fmodules %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-NO-NS --implicit-check-not=unused
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -std=c++17 -emit-llvm -DNS -fmodules %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-NS --implicit-check-not=unused
+
+// Check that we behave sensibly when importing a header containing strong and
+// weak, ordered and unordered global initializers.
+//
+// Our behavior is as follows:
+//
+//  -- for variables with one or more specific points of initialization
+//     (non-template variables, whether or not they are inline or thread_local),
+//     emit them if (and only if) a header containing a point of initialization
+//     is transitively #included / imported.
+//
+//  -- for variables with unordered initialization (any kind of templated
+//     variable -- excluding explicit specializations), emit them if any part
+//     of any module that triggers an instantiation is imported.
+//
+// The intent is to:
+//
+// 1) preserve order of initialization guarantees
+// 2) preserve the behavior of globals with ctors in headers, and specifically
+//    of std::ios_base::Init (do not run the iostreams initializer nor force
+//    linking in the iostreams portion of the static library unless <iostream>
+//    is included)
+// 3) behave conservatively-correctly with regard to unordered initializers: we
+//    might run them in cases where a traditional compilation would not, but
+//    will never fail to run them in cases where a traditional compilation
+//    would do so
+//
+// Perfect handling of unordered initializers would require tracking all
+// submodules containing points of instantiation, which is very hard when those
+// points of instantiation are within definitions that we skip because we
+// already have a (non-visible) definition for the entity:
+//
+// // a.h
+// template<typename> int v = f();
+// inline int get() { return v<int>; }
+//
+// // b.h
+// template<typename> int v = f();
+// inline int get() { return v<int>; }
+//
+// If a.h and b.h are built as a module, we will only have a point of
+// instantiation for v<int> in one of the two headers, because we will only
+// parse one of the two get() functions.
+
+#pragma clang module build m
+module m {
+  module a {
+    header "foo.h" { size 123 mtime 456789 }
+  }
+  module b {}
+}
+
+#pragma clang module contents
+#pragma clang module begin m.a
+inline int non_trivial() { return 3; }
+
+#ifdef NS
+namespace ns {
+#endif
+
+int a = non_trivial();
+inline int b = non_trivial();
+thread_local int c = non_trivial();
+inline thread_local int d = non_trivial();
+
+template<typename U> int e = non_trivial();
+template<typename U> inline int f = non_trivial();
+template<typename U> thread_local int g = non_trivial();
+template<typename U> inline thread_local int h = non_trivial();
+
+inline int unused = 123; // should not be emitted
+
+template<typename T> struct X {
+  static int a;
+  static inline int b = non_trivial();
+  static thread_local int c;
+  static inline thread_local int d = non_trivial();
+
+  template<typename U> static int e;
+  template<typename U> static inline int f = non_trivial();
+  template<typename U> static thread_local int g;
+  template<typename U> static inline thread_local int h = non_trivial();
+
+  static inline int unused = 123; // should not be emitted
+};
+
+template<typename T> int X<T>::a = non_trivial();
+template<typename T> thread_local int X<T>::c = non_trivial();
+template<typename T> template<typename U> int X<T>::e = non_trivial();
+template<typename T> template<typename U> thread_local int X<T>::g = non_trivial();
+
+inline void use(bool b, ...) {
+  if (b) return;
+  use(true, e<int>, f<int>, g<int>, h<int>,
+      X<int>::a, X<int>::b, X<int>::c, X<int>::d,
+      X<int>::e<int>, X<int>::f<int>, X<int>::g<int>, X<int>::h<int>);
+}
+
+#ifdef NS
+}
+#endif
+
+#pragma clang module end
+#pragma clang module endbuild
+
+#if IMPORT == 1
+// Import the module and the m.a submodule; runs the ordered initializers and
+// the unordered initializers.
+#pragma clang module import m.a
+#elif IMPORT == 2
+// Import the module but not the m.a submodule; runs only the unordered
+// initializers.
+#pragma clang module import m.b
+#else
+// Load the module but do not import any submodules; runs only the unordered
+// initializers. FIXME: Should this skip all of them?
+#pragma clang module load m
+#endif
+
+// CHECK-IMPORT-NO-NS-DAG: @[[A:a]] = global i32 0, align 4
+// CHECK-IMPORT-NO-NS-DAG: @[[B:b]] = linkonce_odr global i32 0, comdat, align 4
+// CHECK-IMPORT-NO-NS-DAG: @[[C:c]] = thread_local global i32 0, align 4
+// CHECK-IMPORT-NO-NS-DAG: @[[D:d]] = linkonce_odr thread_local global i32 0, comdat, align 4
+// CHECK-NO-NS-DAG: @[[E:_Z1eIiE]] = linkonce_odr global i32 0, comdat, align 4
+// CHECK-NO-NS-DAG: @[[F:_Z1fIiE]] = linkonce_odr global i32 0, comdat, align 4
+// CHECK-NO-NS-DAG: @[[G:_Z1gIiE]] = linkonce_odr thread_local global i32 0, comdat, align 4
+// CHECK-NO-NS-DAG: @[[H:_Z1hIiE]] = linkonce_odr thread_local global i32 0, comdat, align 4
+
+// CHECK-IMPORT-NS-DAG: @[[A:_ZN2ns1aE]] = global i32 0, align 4
+// CHECK-IMPORT-NS-DAG: @[[B:_ZN2ns1bE]] = linkonce_odr global i32 0, comdat, align 4
+// CHECK-IMPORT-NS-DAG: @[[BG:_ZGVN2ns1bE]] = linkonce_odr global i64 0, comdat($[[B]]), align 8
+// CHECK-IMPORT-NS-DAG: @[[C:_ZN2ns1cE]] = thread_local global i32 0, align 4
+// CHECK-IMPORT-NS-DAG: @[[D:_ZN2ns1dE]] = linkonce_odr thread_local global i32 0, comdat, align 4
+// CHECK-IMPORT-NS-DAG: @[[DG:_ZGVN2ns1dE]] = linkonce_odr thread_local global i64 0, comdat($[[D]]), align 8
+// CHECK-NS-DAG: @[[E:_ZN2ns1eIiEE]] = linkonce_odr global i32 0, comdat, align 4
+// CHECK-NS-DAG: @[[F:_ZN2ns1fIiEE]] = linkonce_odr global i32 0, comdat, align 4
+// CHECK-NS-DAG: @[[G:_ZN2ns1gIiEE]] = linkonce_odr thread_local global i32 0, comdat, align 4
+// CHECK-NS-DAG: @[[H:_ZN2ns1hIiEE]] = linkonce_odr thread_local global i32 0, comdat, align 4
+
+// CHECK-DAG: @[[XA:_ZN(2ns)?1XIiE1aE]] = linkonce_odr global i32 0, comdat, align 4
+// CHECK-DAG: @[[XB:_ZN(2ns)?1XIiE1bE]] = linkonce_odr global i32 0, comdat, align 4
+// CHECK-DAG: @[[XC:_ZN(2ns)?1XIiE1cE]] = linkonce_odr thread_local global i32 0, comdat, align 4
+// CHECK-DAG: @[[XD:_ZN(2ns)?1XIiE1dE]] = linkonce_odr thread_local global i32 0, comdat, align 4
+// CHECK-DAG: @[[XE:_ZN(2ns)?1XIiE1eIiEE]] = linkonce_odr global i32 0, comdat, align 4
+// CHECK-DAG: @[[XF:_ZN(2ns)?1XIiE1fIiEE]] = linkonce_odr global i32 0, comdat, align 4
+// CHECK-DAG: @[[XG:_ZN(2ns)?1XIiE1gIiEE]] = linkonce_odr thread_local global i32 0, comdat, align 4
+// CHECK-DAG: @[[XH:_ZN(2ns)?1XIiE1hIiEE]] = linkonce_odr thread_local global i32 0, comdat, align 4
+
+// It's OK if the order of the first 6 of these changes.
+// CHECK: @llvm.global_ctors = appending global
+// CHECK-SAME: @[[E_INIT:[^,]*]], {{[^@]*}} @[[E]]
+// CHECK-SAME: @[[F_INIT:[^,]*]], {{[^@]*}} @[[F]]
+// CHECK-SAME: @[[XA_INIT:[^,]*]], {{[^@]*}} @[[XA]]
+// CHECK-SAME: @[[XE_INIT:[^,]*]], {{[^@]*}} @[[XE]]
+// CHECK-SAME: @[[XF_INIT:[^,]*]], {{[^@]*}} @[[XF]]
+// CHECK-SAME: @[[XB_INIT:[^,]*]], {{[^@]*}} @[[XB]]
+// CHECK-IMPORT-SAME: @[[TU_INIT:[^,]*]], i8* null }]
+
+// FIXME: Should this use __cxa_guard_acquire?
+// CHECK: define {{.*}} @[[E_INIT]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[E]],
+
+// FIXME: Should this use __cxa_guard_acquire?
+// CHECK: define {{.*}} @[[F_INIT]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[F]],
+
+// CHECK: define {{.*}} @[[G_INIT:__cxx_global.*]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[G]],
+
+// CHECK: define {{.*}} @[[H_INIT:__cxx_global.*]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[H]],
+
+// FIXME: Should this use __cxa_guard_acquire?
+// CHECK: define {{.*}} @[[XA_INIT]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[XA]],
+
+// CHECK: define {{.*}} @[[XC_INIT:__cxx_global.*]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[XC]],
+
+// FIXME: Should this use __cxa_guard_acquire?
+// CHECK: define {{.*}} @[[XE_INIT]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[XE]],
+
+// CHECK: define {{.*}} @[[XG_INIT:__cxx_global.*]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[XG]],
+
+// CHECK: define {{.*}} @[[XH_INIT:__cxx_global.*]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[XH]],
+
+// FIXME: Should this use __cxa_guard_acquire?
+// CHECK: define {{.*}} @[[XF_INIT]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[XF]],
+
+// CHECK: define {{.*}} @[[XD_INIT:__cxx_global.*]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[XD]],
+
+// FIXME: Should this use __cxa_guard_acquire?
+// CHECK: define {{.*}} @[[XB_INIT]]()
+// CHECK: load {{.*}} (i64* @_ZGV
+// CHECK: store {{.*}}, i32* @[[XB]],
+
+// CHECK-IMPORT: define {{.*}} @[[A_INIT:__cxx_global.*]]()
+// CHECK-IMPORT: call i32 @_Z11non_trivialv(
+// CHECK-IMPORT: store {{.*}}, i32* @[[A]],
+
+// CHECK-IMPORT: define {{.*}} @[[B_INIT:__cxx_global.*]]()
+// CHECK-IMPORT: call i32 @__cxa_guard_acquire(i64* @_ZGV
+// CHECK-IMPORT: store {{.*}}, i32* @[[B]],
+
+// CHECK-IMPORT: define {{.*}} @[[C_INIT:__cxx_global.*]]()
+// CHECK-IMPORT: call i32 @_Z11non_trivialv(
+// CHECK-IMPORT: store {{.*}}, i32* @[[C]],
+
+// CHECK-IMPORT: define {{.*}} @[[D_INIT:__cxx_global.*]]()
+// CHECK-IMPORT: load {{.*}} (i64* @_ZGV
+// CHECK-IMPORT: store {{.*}}, i32* @[[D]],
+
+
+// CHECK-IMPORT: define {{.*}} @[[TU_INIT]]()
+// CHECK-IMPORT: call void @[[A_INIT]]()
+// CHECK-IMPORT: call void @[[B_INIT]]()
+
+// CHECK-IMPORT: define {{.*}} @__tls_init()
+// CHECK-IMPORT: call void @[[C_INIT]]()
+// CHECK-IMPORT: call void @[[D_INIT]]()