From 33f3ebc86e7d3afcb65c551feba5bbc2421b42ed Mon Sep 17 00:00:00 2001
From: Anshil Gandhi <95053726+gandhi56@users.noreply.github.com>
Date: Sun, 25 Aug 2024 14:06:29 -0400
Subject: [PATCH] [AMDGPU][LTO] Assume closed world after linking (#105845)

---
 llvm/lib/Target/AMDGPU/AMDGPUAttributor.cpp    |  4 ++++
 llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp |  8 ++++++--
 llvm/test/LTO/AMDGPU/gpu-rdc-amdgpu-attrs.ll   | 10 ++++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/LTO/AMDGPU/gpu-rdc-amdgpu-attrs.ll

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUAttributor.cpp b/llvm/lib/Target/AMDGPU/AMDGPUAttributor.cpp
index d65e0ae92308e6..81932cc2c3c3bc 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUAttributor.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUAttributor.cpp
@@ -1066,6 +1066,10 @@ static bool runImpl(Module &M, AnalysisGetter &AG, TargetMachine &TM,
 
   Attributor A(Functions, InfoCache, AC);
 
+  LLVM_DEBUG(dbgs() << "Module " << M.getName() << " is "
+                    << (AC.IsClosedWorldModule ? "" : "not ")
+                    << "assumed to be a closed world.\n");
+
   for (Function &F : M) {
     if (F.isIntrinsic())
       continue;
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
index 7ac7b3315bb972..307774ea3da9eb 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
@@ -760,8 +760,12 @@ void AMDGPUTargetMachine::registerPassBuilderCallbacks(PassBuilder &PB) {
         // module is partitioned for codegen.
         if (EnableLowerModuleLDS)
           PM.addPass(AMDGPULowerModuleLDSPass(*this));
-        if (EnableAMDGPUAttributor && Level != OptimizationLevel::O0)
-          PM.addPass(AMDGPUAttributorPass(*this));
+
+        if (EnableAMDGPUAttributor && Level != OptimizationLevel::O0) {
+          AMDGPUAttributorOptions Opts;
+          Opts.IsClosedWorld = true;
+          PM.addPass(AMDGPUAttributorPass(*this, Opts));
+        }
       });
 
   PB.registerRegClassFilterParsingCallback(
diff --git a/llvm/test/LTO/AMDGPU/gpu-rdc-amdgpu-attrs.ll b/llvm/test/LTO/AMDGPU/gpu-rdc-amdgpu-attrs.ll
new file mode 100644
index 00000000000000..6966c702e741cc
--- /dev/null
+++ b/llvm/test/LTO/AMDGPU/gpu-rdc-amdgpu-attrs.ll
@@ -0,0 +1,10 @@
+; RUN: opt -O3 -debug-only=amdgpu-attributor -S -o - %s 2>&1 | FileCheck %s --check-prefix=PRE-LINK
+; RUN: opt -passes="lto<O3>" -debug-only=amdgpu-attributor -S -o - %s 2>&1 | 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
+}