[llvm] [ctxprof] Override type of instrumentation if `-profile-context-root` is specified (PR #128940)

[Mircea Trofin via llvm-commits]

https://github.com/mtrofin updated https://github.com/llvm/llvm-project/pull/128940

>From 14a695874d9204a1a5680df42d47e80ba3971d8a Mon Sep 17 00:00:00 2001
From: Mircea Trofin <mtrofin at google.com>
Date: Wed, 26 Feb 2025 12:05:45 -0800
Subject: [PATCH] [ctxprof] Override type of instrumentation if
 `-profile-context-root` is specified

---
 llvm/lib/Passes/PassBuilderPipelines.cpp         |  8 ++++----
 .../PGOProfile/ctx-instrumentation-optin.ll      | 16 ++++++++++++++++
 2 files changed, 20 insertions(+), 4 deletions(-)
 create mode 100644 llvm/test/Transforms/PGOProfile/ctx-instrumentation-optin.ll

diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index d4c3fe9562f9e..546a5eb1ec283 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -1206,7 +1206,10 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
 
   // We already asserted this happens in non-FullLTOPostLink earlier.
   const bool IsPreLink = Phase != ThinOrFullLTOPhase::ThinLTOPostLink;
-  const bool IsPGOPreLink = PGOOpt && IsPreLink;
+  // Enable contextual profiling instrumentation.
+  const bool IsCtxProfGen =
+      IsPreLink && PGOCtxProfLoweringPass::isCtxIRPGOInstrEnabled();
+  const bool IsPGOPreLink = !IsCtxProfGen && PGOOpt && IsPreLink;
   const bool IsPGOInstrGen =
       IsPGOPreLink && PGOOpt->Action == PGOOptions::IRInstr;
   const bool IsPGOInstrUse =
@@ -1217,9 +1220,6 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
   assert(!(IsPGOInstrGen && PGOCtxProfLoweringPass::isCtxIRPGOInstrEnabled()) &&
          "Enabling both instrumented PGO and contextual instrumentation is not "
          "supported.");
-  // Enable contextual profiling instrumentation.
-  const bool IsCtxProfGen = !IsPGOInstrGen && IsPreLink &&
-                            PGOCtxProfLoweringPass::isCtxIRPGOInstrEnabled();
   const bool IsCtxProfUse =
       !UseCtxProfile.empty() && Phase == ThinOrFullLTOPhase::ThinLTOPreLink;
 
diff --git a/llvm/test/Transforms/PGOProfile/ctx-instrumentation-optin.ll b/llvm/test/Transforms/PGOProfile/ctx-instrumentation-optin.ll
new file mode 100644
index 0000000000000..f749e3e526b9d
--- /dev/null
+++ b/llvm/test/Transforms/PGOProfile/ctx-instrumentation-optin.ll
@@ -0,0 +1,16 @@
+; REQUIRES: linux
+;
+; RUN: opt -O2 -debug-pass-manager -S -pgo-kind=pgo-instr-gen-pipeline -profile-file='temp' \
+; RUN:  < %s  2>&1 | FileCheck %s --check-prefixes=COMMON,PGO
+; RUN: opt -O2 -debug-pass-manager -S -pgo-kind=pgo-instr-gen-pipeline -profile-file='temp' \
+; RUN:  -profile-context-root=something < %s 2>&1 | FileCheck %s --check-prefixes=COMMON,CTXPROF
+
+; COMMON:   Running pass: PGOInstrumentationGen
+; COMMON:   Invalidating analysis: InnerAnalysisManagerProxy<FunctionAnalysisManager, Module>
+; COMMON:   Invalidating analysis: LazyCallGraphAnalysis
+; COMMON:   Invalidating analysis: InnerAnalysisManagerProxy<CGSCCAnalysisManager, Module>
+; CTXPROF:  Running pass: AssignGUIDPass
+; CTXPROF:  Running pass: NoinlineNonPrevailing
+; COMMON:   Running analysis: InnerAnalysisManagerProxy<FunctionAnalysisManager, Module>
+; PGO:      Running pass: InstrProfilingLoweringPass
+; CTXPROF:  Running pass: PGOCtxProfLoweringPass