[llvm] [ctxprof] Option to move a whole tree to its own module (PR #133992)

[Mircea Trofin via llvm-commits]

https://github.com/mtrofin updated https://github.com/llvm/llvm-project/pull/133992

>From 1b0c0a478e1f5443100325cf2e2b5f2cc40649b6 Mon Sep 17 00:00:00 2001
From: Mircea Trofin <mtrofin at google.com>
Date: Tue, 1 Apr 2025 14:28:20 -0700
Subject: [PATCH] [ctxprof] Option to move a whole tree to its own module

---
 llvm/lib/Transforms/IPO/FunctionImport.cpp    | 32 +++++++++--
 .../ThinLTO/X86/ctxprof-separate-module.ll    | 56 +++++++++++++++++++
 2 files changed, 83 insertions(+), 5 deletions(-)
 create mode 100644 llvm/test/ThinLTO/X86/ctxprof-separate-module.ll

diff --git a/llvm/lib/Transforms/IPO/FunctionImport.cpp b/llvm/lib/Transforms/IPO/FunctionImport.cpp
index f0daf1a558316..cfefc0e8c43a8 100644
--- a/llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -38,6 +38,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/JSON.h"
+#include "llvm/Support/Path.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/IPO/Internalize.h"
@@ -175,6 +176,12 @@ static cl::opt<std::string> WorkloadDefinitions(
 
 extern cl::opt<std::string> UseCtxProfile;
 
+static cl::opt<bool> CtxprofMoveRootsToOwnModule(
+    "thinlto-move-ctxprof-trees",
+    cl::desc("Move contextual profiling roots and the graphs under them in "
+             "their own module."),
+    cl::Hidden, cl::init(false));
+
 namespace llvm {
 extern cl::opt<bool> EnableMemProfContextDisambiguation;
 }
@@ -535,7 +542,14 @@ class WorkloadImportsManager : public ModuleImportsManager {
   computeImportForModule(const GVSummaryMapTy &DefinedGVSummaries,
                          StringRef ModName,
                          FunctionImporter::ImportMapTy &ImportList) override {
-    auto SetIter = Workloads.find(ModName);
+    StringRef Filename = ModName;
+    if (CtxprofMoveRootsToOwnModule) {
+      Filename = sys::path::filename(ModName);
+      // Drop the file extension.
+      Filename = Filename.substr(0, Filename.find_last_of('.'));
+    }
+    auto SetIter = Workloads.find(Filename);
+
     if (SetIter == Workloads.end()) {
       LLVM_DEBUG(dbgs() << "[Workload] " << ModName
                         << " does not contain the root of any context.\n");
@@ -748,10 +762,18 @@ class WorkloadImportsManager : public ModuleImportsManager {
                           << RootVI.getSummaryList().size() << ". Skipping.\n");
         continue;
       }
-      StringRef RootDefiningModule =
-          RootVI.getSummaryList().front()->modulePath();
-      LLVM_DEBUG(dbgs() << "[Workload] Root defining module for " << RootGuid
-                        << " is : " << RootDefiningModule << "\n");
+      std::string RootDefiningModule =
+          RootVI.getSummaryList().front()->modulePath().str();
+      if (CtxprofMoveRootsToOwnModule) {
+        RootDefiningModule = std::to_string(RootGuid);
+        LLVM_DEBUG(
+            dbgs() << "[Workload] Moving " << RootGuid
+                   << " to a module with the filename without extension : "
+                   << RootDefiningModule << "\n");
+      } else {
+        LLVM_DEBUG(dbgs() << "[Workload] Root defining module for " << RootGuid
+                          << " is : " << RootDefiningModule << "\n");
+      }
       auto &Set = Workloads[RootDefiningModule];
       Root.getContainedGuids(ContainedGUIDs);
       for (auto Guid : ContainedGUIDs)
diff --git a/llvm/test/ThinLTO/X86/ctxprof-separate-module.ll b/llvm/test/ThinLTO/X86/ctxprof-separate-module.ll
new file mode 100644
index 0000000000000..c7891d336cc89
--- /dev/null
+++ b/llvm/test/ThinLTO/X86/ctxprof-separate-module.ll
@@ -0,0 +1,56 @@
+; Test workload based importing via -thinlto-pgo-ctx-prof with moving the whole
+; graph to a new module.
+; Use external linkage symbols so we don't depend on module paths which are
+; used when computing the GUIDs of internal linkage symbols.
+;
+; Set up
+; RUN: rm -rf %t
+; RUN: mkdir -p %t
+; RUN: split-file %s %t
+;
+; RUN: opt -module-summary -passes=assign-guid,ctx-instr-gen %t/m1.ll -o %t/m1.bc
+; RUN: opt -module-summary -passes=assign-guid,ctx-instr-gen %t/m2.ll -o %t/m2.bc
+; RUN: opt -module-summary -passes=assign-guid,ctx-instr-gen %t/6019442868614718803.ll -o %t/6019442868614718803.bc
+
+; RUN: llvm-ctxprof-util fromYAML --input %t/ctxprof.yaml --output %t/ctxprof.bitstream
+; RUN: llvm-lto2 run %t/m1.bc %t/m2.bc %t/6019442868614718803.bc -thinlto-move-ctxprof-trees \
+; RUN:  -o %t/result.o -save-temps \
+; RUN:  -use-ctx-profile=%t/ctxprof.bitstream \
+; RUN:  -r %t/m1.bc,m1_f1,plx \
+; RUN:  -r %t/m2.bc,m2_f1,plx
+; RUN: llvm-dis %t/result.o.3.3.import.bc -o - | FileCheck %s
+;
+;
+; CHECK: m1_f1()
+; CHECK: m2_f1()
+;
+;--- ctxprof.yaml
+Contexts: 
+  -
+    Guid: 6019442868614718803
+    TotalRootEntryCount: 5
+    Counters: [1]
+    Callsites:  
+      - -
+          Guid: 15593096274670919754
+          Counters: [1]
+
+;--- m1.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-linux-gnu"
+
+define dso_local void @m1_f1() {
+  ret void
+}
+
+;--- m2.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-linux-gnu"
+
+define dso_local void @m2_f1() {
+  ret void
+}
+
+;--- 6019442868614718803.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-linux-gnu"