[llvm] [nfc] Clarify when the various PGO instrumentation passes run (PR #92330)

[Mircea Trofin via llvm-commits]

https://github.com/mtrofin created https://github.com/llvm/llvm-project/pull/92330

The code seems easier to read if it's centered on what the user wants rather than combinations of whatever internal variables.

>From 63a72bc4c6d622c079d431a920ffeff8d400d54d 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] [nfc] Clarify when the various PGO instrumentation passes run

The code seems easier to read if it's centered on what the user
wants rather than combinations of whatever internal variables.
---
 llvm/lib/Passes/PassBuilderPipelines.cpp | 45 +++++++++++++++---------
 1 file changed, 28 insertions(+), 17 deletions(-)

diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 72f273972f2f7..b838f083c6e0d 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -835,10 +835,6 @@ void PassBuilder::addPGOInstrPasses(ModulePassManager &MPM,
         PTO.EagerlyInvalidateAnalyses));
   }
 
-  if (PGOCtxProfLoweringPass::isContextualIRPGOEnabled()) {
-    MPM.addPass(PGOCtxProfLoweringPass());
-    return;
-  }
   // Add the profile lowering pass.
   InstrProfOptions Options;
   if (!ProfileFile.empty())
@@ -1145,29 +1141,44 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
   MPM.addPass(createModuleToFunctionPassAdaptor(std::move(GlobalCleanupPM),
                                                 PTO.EagerlyInvalidateAnalyses));
 
-  // Invoke the pre-inliner passes for instrumentation PGO or MemProf.
-  if (PGOOpt && Phase != ThinOrFullLTOPhase::ThinLTOPostLink &&
-      (PGOOpt->Action == PGOOptions::IRInstr ||
-       PGOOpt->Action == PGOOptions::IRUse || !PGOOpt->MemoryProfile.empty()))
+  const bool IsPreLink = Phase != ThinOrFullLTOPhase::ThinLTOPostLink;
+  const bool IsPGOPreLink = PGOOpt && IsPreLink;
+  const bool IsPGOInstrGen =
+      IsPGOPreLink && PGOOpt->Action == PGOOptions::IRInstr;
+  const bool IsPGOInstrUse =
+      IsPGOPreLink && PGOOpt->Action == PGOOptions::IRUse;
+  const bool IsMemprof = 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 || IsMemprof || IsCtxProfGen)
     addPreInlinerPasses(MPM, Level, Phase);
 
   // Add all the requested passes for instrumentation PGO, if requested.
-  if (PGOOpt && Phase != ThinOrFullLTOPhase::ThinLTOPostLink &&
-      (PGOOpt->Action == PGOOptions::IRInstr ||
-       PGOOpt->Action == PGOOptions::IRUse)) {
+  if (IsPGOInstrGen || IsPGOInstrUse)
     addPGOInstrPasses(MPM, Level,
-                      /*RunProfileGen=*/PGOOpt->Action == PGOOptions::IRInstr,
+                      /*RunProfileGen=*/IsPGOInstrGen,
                       /*IsCS=*/false, PGOOpt->AtomicCounterUpdate,
                       PGOOpt->ProfileFile, PGOOpt->ProfileRemappingFile,
                       PGOOpt->FS);
-    MPM.addPass(PGOIndirectCallPromotion(false, false));
+
+  if (IsCtxProfGen) {
+    MPM.addPass(PGOInstrumentationGen(false));
+    MPM.addPass(PGOCtxProfLoweringPass());
   }
-  if (PGOOpt && Phase != ThinOrFullLTOPhase::ThinLTOPostLink &&
-      PGOOpt->CSAction == PGOOptions::CSIRInstr)
+
+  if (IsPGOInstrGen || IsPGOInstrUse || IsCtxProfGen)
+    MPM.addPass(PGOIndirectCallPromotion(false, false));
+
+  if (IsCtxProfGen)
+    MPM.addPass(PGOCtxProfLoweringPass());
+
+  if (IsPGOPreLink && PGOOpt->CSAction == PGOOptions::CSIRInstr)
     MPM.addPass(PGOInstrumentationGenCreateVar(PGOOpt->CSProfileGenFile));
 
-  if (PGOOpt && Phase != ThinOrFullLTOPhase::ThinLTOPostLink &&
-      !PGOOpt->MemoryProfile.empty())
+  if (IsMemprof)
     MPM.addPass(MemProfUsePass(PGOOpt->MemoryProfile, PGOOpt->FS));
 
   // Synthesize function entry counts for non-PGO compilation.