[AMDGPU][LTO] Assume closed world after linking

Change-Id: I7d8fa4251c80a6f815f55a0998677d18ade25b72

Author: gandhi56

llvm/lib/Target/AMDGPU/AMDGPUAttributor.cpp

@@ -1066,6 +1066,10 @@ static bool runImpl(Module &M, AnalysisGetter &AG, TargetMachine &TM,
 
   Attributor A(Functions, InfoCache, AC);
 
+  dbgs() << "Module " << M.getName() << " is "
+                    << (AC.IsClosedWorldModule ? "" : "not ")
+                    << "assumed to be a closed world.\n";
+
   for (Function &F : M) {
     if (F.isIntrinsic())
       continue;

llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

@@ -760,8 +760,11 @@ void AMDGPUTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
         // module is partitioned for codegen.
         if (EnableLowerModuleLDS)
           PM.addPass(AMDGPULowerModuleLDSPass(*this));
+
+        AMDGPUAttributorOptions Opts;
+        Opts.IsClosedWorld = true;
         if (EnableAMDGPUAttributor && Level != OptimizationLevel::O0)
-          PM.addPass(AMDGPUAttributorPass(*this));
+          PM.addPass(AMDGPUAttributorPass(*this, Opts));
       });
 
   PB.registerRegClassFilterParsingCallback(

llvm/test/LTO/AMDGPU/gpu-rdc-amdgpu-attrs.ll

@@ -0,0 +1,10 @@
+; RUN: opt -O3 -debug-only=amdgpu-attributor -S -o - %s | FileCheck %s --check-prefix=PRE-LINK
+; RUN: opt -passes="lto<O3>" -debug-only=amdgpu-attributor -S -o - %s | FileCheck %s --check-prefix=POST-LINK
+
+target triple = "amdgcn-amd-amdhsa"
+
+; PRE-LINK: Module {{.*}} is not assumed to be a closed world.
+; POST-LINK: Module {{.*}} is assumed to be a closed world.
+define hidden noundef i32 @_Z3foov() {
+  ret i32 1
+}