[OPENMP] Mark global tors/dtors as used.

If the global variables are marked as declare target and they need
ctors/dtors, these ctors/dtors are emitted and then invoked by the
offloading runtime library. They are not explicitly used in the emitted
code and thus can be optimized out. Patch marks these functions as used,
so the optimizer cannot remove these function during the optimization
phase.

llvm-svn: 331879

diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index 59c0540..35f27b2 100644 (file)
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -2686,6 +2686,7 @@ bool CGOpenMPRuntime::emitDeclareTargetVarDefinition(const VarDecl *VD,
       CtorCGF.FinishFunction();
       Ctor = Fn;
       ID = llvm::ConstantExpr::getBitCast(Fn, CGM.Int8PtrTy);
+      CGM.addUsedGlobal(cast<llvm::GlobalValue>(Ctor));
     } else {
       Ctor = new llvm::GlobalVariable(
           CGM.getModule(), CGM.Int8Ty, /*isConstant=*/true,
@@ -2724,6 +2725,7 @@ bool CGOpenMPRuntime::emitDeclareTargetVarDefinition(const VarDecl *VD,
       DtorCGF.FinishFunction();
       Dtor = Fn;
       ID = llvm::ConstantExpr::getBitCast(Fn, CGM.Int8PtrTy);
+      CGM.addUsedGlobal(cast<llvm::GlobalValue>(Dtor));
     } else {
       Dtor = new llvm::GlobalVariable(
           CGM.getModule(), CGM.Int8Ty, /*isConstant=*/true,

diff --git a/clang/test/OpenMP/declare_target_codegen.cpp b/clang/test/OpenMP/declare_target_codegen.cpp
index f6ee670..02ac148 100644 (file)
--- a/clang/test/OpenMP/declare_target_codegen.cpp
+++ b/clang/test/OpenMP/declare_target_codegen.cpp
@@ -17,10 +17,13 @@
 // CHECK-DAG: @b = global i32 15,
 // CHECK-DAG: @d = global i32 0,
 // CHECK-DAG: @c = external global i32,
+// CHECK-DAG: @globals = global %struct.S zeroinitializer,
+// CHECK-DAG: @llvm.used = appending global [1 x i8*] [i8* bitcast (void ()* @__omp_offloading__{{.+}}_globals_l[[@LINE+41]]_ctor to i8*)], section "llvm.metadata"
 
 // CHECK-DAG: define {{.*}}i32 @{{.*}}{{foo|bar|baz2|baz3|FA|f_method}}{{.*}}()
 // CHECK-DAG: define {{.*}}void @{{.*}}TemplateClass{{.*}}(%class.TemplateClass* %{{.*}})
 // CHECK-DAG: define {{.*}}i32 @{{.*}}TemplateClass{{.*}}f_method{{.*}}(%class.TemplateClass* %{{.*}})
+// CHECK-DAG: define {{.*}}void @__omp_offloading__{{.*}}_globals_l[[@LINE+36]]_ctor()
 
 #ifndef HEADER
 #define HEADER
@@ -56,6 +59,7 @@ struct S {
 int foo() { return 0; }
 int b = 15;
 int d;
+S globals(d);
 #pragma omp end declare target
 int c;