[Serialization] Read the initializer for interesting static variables before consuming it (#92353)

Close #91418

Since we load the variable's initializers lazily, it'd be problematic if
the initializers dependent on each other. So here we try to load the
initializers of static variables to make sure they are passed to code
generator by order. If we read any thing interesting, we would consume
that before emitting the current declaration.

Author: ChuanqiXu9

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -4186,12 +4186,35 @@ void ASTReader::PassInterestingDeclsToConsumer() {
     GetDecl(ID);
   EagerlyDeserializedDecls.clear();
 
-  while (!PotentiallyInterestingDecls.empty()) {
-    Decl *D = PotentiallyInterestingDecls.front();
-    PotentiallyInterestingDecls.pop_front();
+  auto ConsumingPotentialInterestingDecls = [this]() {
+    while (!PotentiallyInterestingDecls.empty()) {
+      Decl *D = PotentiallyInterestingDecls.front();
+      PotentiallyInterestingDecls.pop_front();
+      if (isConsumerInterestedIn(D))
+        PassInterestingDeclToConsumer(D);
+    }
+  };
+  std::deque<Decl *> MaybeInterestingDecls =
+      std::move(PotentiallyInterestingDecls);
+  assert(PotentiallyInterestingDecls.empty());
+  while (!MaybeInterestingDecls.empty()) {
+    Decl *D = MaybeInterestingDecls.front();
+    MaybeInterestingDecls.pop_front();
+    // Since we load the variable's initializers lazily, it'd be problematic
+    // if the initializers dependent on each other. So here we try to load the
+    // initializers of static variables to make sure they are passed to code
+    // generator by order. If we read anything interesting, we would consume
+    // that before emitting the current declaration.
+    if (auto *VD = dyn_cast<VarDecl>(D);
+        VD && VD->isFileVarDecl() && !VD->isExternallyVisible())
+      VD->getInit();
+    ConsumingPotentialInterestingDecls();
     if (isConsumerInterestedIn(D))
       PassInterestingDeclToConsumer(D);
   }
+
+  // If we add any new potential interesting decl in the last call, consume it.
+  ConsumingPotentialInterestingDecls();
 }
 
 void ASTReader::loadDeclUpdateRecords(PendingUpdateRecord &Record) {

clang/test/Modules/pr91418.cppm

@@ -0,0 +1,65 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 -x c++-header %t/foo.h \
+// RUN:     -emit-pch -o %t/foo.pch
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %t/use.cpp -include-pch \
+// RUN:     %t/foo.pch -emit-llvm -o - | FileCheck %t/use.cpp
+
+//--- foo.h
+#ifndef FOO_H
+#define FOO_H
+typedef float __m128 __attribute__((__vector_size__(16), __aligned__(16)));
+
+static __inline__ __m128 __attribute__((__always_inline__, __min_vector_width__(128)))
+_mm_setr_ps(float __z, float __y, float __x, float __w)
+{
+  return __extension__ (__m128){ __z, __y, __x, __w };
+}
+
+typedef __m128 VR;
+
+inline VR MakeVR( float X, float Y, float Z, float W )
+{
+ return _mm_setr_ps( X, Y, Z, W );
+}
+
+extern "C" float sqrtf(float);
+
+namespace VectorSinConstantsSSE
+{
+  float a = (16 * sqrtf(0.225f));
+  VR A = MakeVR(a, a, a, a);
+  static const float b = (16 * sqrtf(0.225f));
+  static const VR B = MakeVR(b, b, b, b);
+}
+
+#endif // FOO_H
+
+//--- use.cpp
+#include "foo.h"
+float use() {
+    return VectorSinConstantsSSE::A[0] + VectorSinConstantsSSE::A[1] +
+           VectorSinConstantsSSE::A[2] + VectorSinConstantsSSE::A[3] +
+           VectorSinConstantsSSE::B[0] + VectorSinConstantsSSE::B[1] +
+           VectorSinConstantsSSE::B[2] + VectorSinConstantsSSE::B[3];
+}
+
+// CHECK: define{{.*}}@__cxx_global_var_init(
+// CHECK: store{{.*}}, ptr @_ZN21VectorSinConstantsSSE1aE
+
+// CHECK: define{{.*}}@__cxx_global_var_init.1(
+// CHECK: store{{.*}}, ptr @_ZN21VectorSinConstantsSSE1AE
+
+// CHECK: define{{.*}}@__cxx_global_var_init.2(
+// CHECK: store{{.*}}, ptr @_ZN21VectorSinConstantsSSEL1BE
+
+// CHECK: define{{.*}}@__cxx_global_var_init.3(
+// CHECK: store{{.*}}, ptr @_ZN21VectorSinConstantsSSEL1bE
+
+// CHECK: @_GLOBAL__sub_I_use.cpp
+// CHECK: call{{.*}}@__cxx_global_var_init(
+// CHECK: call{{.*}}@__cxx_global_var_init.1(
+// CHECK: call{{.*}}@__cxx_global_var_init.3(
+// CHECK: call{{.*}}@__cxx_global_var_init.2(