[llvm] [ctx_profile] Decouple ctx instrumentation from PGOOpt (PR #92445)

[Mircea Trofin via llvm-commits]

https://github.com/mtrofin updated https://github.com/llvm/llvm-project/pull/92445

>From 1dbe45a50e7010e4907b05fac225063167c7912b Mon Sep 17 00:00:00 2001
From: Mircea Trofin <mtrofin at google.com>
Date: Wed, 15 May 2024 17:11:56 -0700
Subject: [PATCH 1/2] [ctx_profile] Decouple ctx  instrumentation from PGOOpt

We currently don't support passing files and don't need frontend involvment either.
---
 llvm/lib/Passes/PassBuilderPipelines.cpp | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 682bdefbd5243..dd1752d59e65a 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -839,10 +839,6 @@ void PassBuilder::addPGOInstrPasses(ModulePassManager &MPM,
   MPM.addPass(PGOInstrumentationGen(IsCS));
 
   addPostPGOLoopRotation(MPM, Level);
-  if (PGOCtxProfLoweringPass::isContextualIRPGOEnabled()) {
-    MPM.addPass(PGOCtxProfLoweringPass());
-    return;
-  }
   // Add the profile lowering pass.
   InstrProfOptions Options;
   if (!ProfileFile.empty())
@@ -1157,8 +1153,12 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
   const bool IsPGOInstrUse =
       IsPGOPreLink && PGOOpt->Action == PGOOptions::IRUse;
   const bool IsMemprofUse = IsPGOPreLink && !PGOOpt->MemoryProfile.empty();
+  // We don't want to mix pgo ctx gen and pgo gen; we also don't currently
+  // enable ctx profiling from the frontend.
+  const bool IsCtxProfGen = !IsPGOInstrGen && IsPreLink &&
+                            PGOCtxProfLoweringPass::isContextualIRPGOEnabled();
 
-  if (IsPGOInstrGen || IsPGOInstrUse || IsMemprofUse)
+  if (IsPGOInstrGen || IsPGOInstrUse || IsMemprofUse || IsCtxProfGen)
     addPreInlinerPasses(MPM, Level, Phase);
 
   // Add all the requested passes for instrumentation PGO, if requested.
@@ -1168,9 +1168,13 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
                       /*IsCS=*/false, PGOOpt->AtomicCounterUpdate,
                       PGOOpt->ProfileFile, PGOOpt->ProfileRemappingFile,
                       PGOOpt->FS);
+  } else if (IsCtxProfGen) {
+    MPM.addPass(PGOInstrumentationGen(false));
+    addPostPGOLoopRotation(MPM, Level);
+    MPM.addPass(PGOCtxProfLoweringPass());
   }
 
-  if (IsPGOInstrGen || IsPGOInstrUse)
+  if (IsPGOInstrGen || IsPGOInstrUse || IsCtxProfGen)
     MPM.addPass(PGOIndirectCallPromotion(false, false));
 
   if (IsPGOPreLink && PGOOpt->CSAction == PGOOptions::CSIRInstr)

>From b1f443a2f0a7644c7e5cf5294cebfc88beba2715 Mon Sep 17 00:00:00 2001
From: Mircea Trofin <mtrofin at google.com>
Date: Thu, 16 May 2024 13:38:48 -0700
Subject: [PATCH 2/2] feedback

---
 llvm/lib/Passes/PassBuilderPipelines.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index dd1752d59e65a..1892e16a06528 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -1155,6 +1155,11 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
   const bool IsMemprofUse = IsPGOPreLink && !PGOOpt->MemoryProfile.empty();
   // We don't want to mix pgo ctx gen and pgo gen; we also don't currently
   // enable ctx profiling from the frontend.
+  assert(
+      !(IsPGOInstrGen && PGOCtxProfLoweringPass::isContextualIRPGOEnabled()) &&
+      "Enabling both instrumented FDO and contextual instrumentation is not "
+      "supported.");
+  // Enable contextual profiling instrumentation.
   const bool IsCtxProfGen = !IsPGOInstrGen && IsPreLink &&
                             PGOCtxProfLoweringPass::isContextualIRPGOEnabled();