[OpenMP] Fix the linkage for kernel environment global variable

This patch fixes the issue that multiple definition of kernel environment global
variables can occur because of wrong linkage.

Fixes llvm#64284.

Reviewed By: jhuber6

Differential Revision: https://reviews.llvm.org/D156955

Author: shiltian

llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

@@ -4040,7 +4040,7 @@ OpenMPIRBuilder::createTargetInit(const LocationDescription &Loc, bool IsSPMD) {
       ConstantStruct::get(DynamicEnvironment, {DebugIndentionLevelVal});
   Constant *DynamicEnvironmentGV = new GlobalVariable(
       M, DynamicEnvironment, /* IsConstant */ false,
-      GlobalValue::InternalLinkage, DynamicEnvironmentInitializer,
+      GlobalValue::WeakODRLinkage, DynamicEnvironmentInitializer,
       DynamicEnvironmentName,
       /* InsertBefore */ nullptr, llvm::GlobalValue::NotThreadLocal,
       DL.getDefaultGlobalsAddressSpace());
@@ -4062,7 +4062,7 @@ OpenMPIRBuilder::createTargetInit(const LocationDescription &Loc, bool IsSPMD) {
                          });
   Twine KernelEnvironmentName = KernelName + "_kernel_environment";
   Constant *KernelEnvironmentGV = new GlobalVariable(
-      M, KernelEnvironment, /* IsConstant */ true, GlobalValue::ExternalLinkage,
+      M, KernelEnvironment, /* IsConstant */ true, GlobalValue::WeakODRLinkage,
       KernelEnvironmentInitializer, KernelEnvironmentName,
       /* InsertBefore */ nullptr, llvm::GlobalValue::NotThreadLocal,
       DL.getDefaultGlobalsAddressSpace());

mlir/test/Target/LLVMIR/omptarget-region-device-llvm.mlir

@@ -25,8 +25,8 @@ module attributes {omp.is_target_device = true} {
 
 // CHECK:      @[[SRC_LOC:.*]] = private unnamed_addr constant [23 x i8] c"{{[^"]*}}", align 1
 // CHECK:      @[[IDENT:.*]] = private unnamed_addr constant %struct.ident_t { i32 0, i32 2, i32 0, i32 22, ptr @[[SRC_LOC]] }, align 8
-// CHECK:      @[[DYNA_ENV:.*]] = internal global %struct.DynamicEnvironmentTy zeroinitializer
-// CHECK:      @[[KERNEL_ENV:.*]] = constant %struct.KernelEnvironmentTy { %struct.ConfigurationEnvironmentTy { i8 1, i8 1, i8 1 }, ptr @[[IDENT]], ptr @[[DYNA_ENV]] }
+// CHECK:      @[[DYNA_ENV:.*]] = weak_odr global %struct.DynamicEnvironmentTy zeroinitializer
+// CHECK:      @[[KERNEL_ENV:.*]] = weak_odr constant %struct.KernelEnvironmentTy { %struct.ConfigurationEnvironmentTy { i8 1, i8 1, i8 1 }, ptr @[[IDENT]], ptr @[[DYNA_ENV]] }
 // CHECK:      define weak_odr protected void @__omp_offloading_{{[^_]+}}_{{[^_]+}}_omp_target_region__l{{[0-9]+}}(ptr %[[ADDR_A:.*]], ptr %[[ADDR_B:.*]], ptr %[[ADDR_C:.*]])
 // CHECK:        %[[INIT:.*]] = call i32 @__kmpc_target_init(ptr @[[KERNEL_ENV]])
 // CHECK-NEXT:   %[[CMP:.*]] = icmp eq i32 %3, -1