[PATCH] D122504: [OpenMP] Make Ctor / Dtor functions have external visibility

[Joseph Huber via Phabricator via cfe-commits]

jhuber6 created this revision.
jhuber6 added reviewers: jdoerfert, JonChesterfield, ronlieb, ABataev.
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The default construction of constructor functions by LLVM tends to make
them have internal linkage. When we call a ctor / dtor function in the
target region we are actually creating a kernel that is called at
registration. Because the ctor is a kernel we need to make sure it's
externally visible so we can actually call it. This prevented AMDGPU
from correctly using constructors while NVPTX could use them simply
because it ignored internal visibility.

Fixes #54091


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D122504

Files:
  clang/lib/CodeGen/CGOpenMPRuntime.cpp
  clang/test/OpenMP/nvptx_declare_target_var_ctor_dtor_codegen.cpp


Index: clang/test/OpenMP/nvptx_declare_target_var_ctor_dtor_codegen.cpp
===================================================================
--- clang/test/OpenMP/nvptx_declare_target_var_ctor_dtor_codegen.cpp
+++ clang/test/OpenMP/nvptx_declare_target_var_ctor_dtor_codegen.cpp
@@ -44,7 +44,7 @@
 static int c = foo() + bar() + baz();
 #pragma omp declare target (c)
 // HOST-DAG: @[[C_CTOR:__omp_offloading__.+_c_l44_ctor]] = private constant i8 0
-// DEVICE-DAG: define internal void [[C_CTOR:@__omp_offloading__.+_c_l44_ctor]]()
+// DEVICE-DAG: define weak_odr dso_local void [[C_CTOR:@__omp_offloading__.+_c_l44_ctor]]()
 // DEVICE-DAG: call noundef i32 [[FOO]]()
 // DEVICE-DAG: call noundef i32 [[BAR]]()
 // DEVICE-DAG: call noundef i32 [[BAZ]]()
@@ -61,14 +61,14 @@
 S cd = doo() + car() + caz() + baz();
 #pragma omp end declare target
 // HOST-DAG: @[[CD_CTOR:__omp_offloading__.+_cd_l61_ctor]] = private constant i8 0
-// DEVICE-DAG: define internal void [[CD_CTOR:@__omp_offloading__.+_cd_l61_ctor]]()
+// DEVICE-DAG: define weak_odr dso_local void [[CD_CTOR:@__omp_offloading__.+_cd_l61_ctor]]()
 // DEVICE-DAG: call noundef i32 [[DOO]]()
 // DEVICE-DAG: call noundef i32 [[CAR]]()
 // DEVICE-DAG: call noundef i32 [[CAZ]]()
 // DEVICE-DAG: ret void
 
 // HOST-DAG: @[[CD_DTOR:__omp_offloading__.+_cd_l61_dtor]] = private constant i8 0
-// DEVICE-DAG: define internal void [[CD_DTOR:@__omp_offloading__.+_cd_l61_dtor]]()
+// DEVICE-DAG: define weak_odr dso_local void [[CD_DTOR:@__omp_offloading__.+_cd_l61_dtor]]()
 // DEVICE-DAG: call void
 // DEVICE-DAG: ret void
 
Index: clang/lib/CodeGen/CGOpenMPRuntime.cpp
===================================================================
--- clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -3022,6 +3022,13 @@
     // This could happen if the device compilation is invoked standalone.
     if (!hasTargetRegionEntryInfo(DeviceID, FileID, ParentName, LineNum))
       return;
+
+    // If we are registering a ctor / dtor we need to make sure it's externally
+    // visible so we can call it from the host.
+    if (Flags == OMPTargetRegionEntryCtor || Flags == OMPTargetRegionEntryDtor)
+      if (llvm::GlobalValue *GV = dyn_cast<llvm::GlobalValue>(Addr))
+        GV->setLinkage(llvm::GlobalValue::WeakODRLinkage);
+
     auto &Entry =
         OffloadEntriesTargetRegion[DeviceID][FileID][ParentName][LineNum];
     Entry.setAddress(Addr);


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