[hot-cold-split] Only perform splitting in ThinLTO backend post-link

Summary:
Fix the new PM to only perform hot cold splitting once during ThinLTO,
by skipping it in the pre-link phase.

This was already fixed in the old PM by the move of the hot cold split
pass later (after the early return when PrepareForThinLTO) by r344869.

Reviewers: vsk, sebpop, hiraditya

Subscribers: mehdi_amini, inglorion, eraman, steven_wu, dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D53611

llvm-svn: 345096

llvm/lib/Passes/PassBuilder.cpp

@@ -710,7 +710,9 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
   MainCGPipeline.addPass(createCGSCCToFunctionPassAdaptor(
       buildFunctionSimplificationPipeline(Level, Phase, DebugLogging)));
 
-  if (EnableHotColdSplit)
+  // We only want to do hot cold splitting once for ThinLTO, during the
+  // post-link ThinLTO.
+  if (EnableHotColdSplit && Phase != ThinLTOPhase::PreLink)
     MPM.addPass(HotColdSplittingPass());
 
   for (auto &C : CGSCCOptimizerLateEPCallbacks)

llvm/test/Other/new-pm-thinlto-defaults.ll

@@ -26,6 +26,10 @@
 ; RUN: opt -disable-verify -debug-pass-manager -new-pm-debug-info-for-profiling \
 ; RUN:     -passes='thinlto-pre-link<O2>,name-anon-globals' -S  %s 2>&1 \
 ; RUN:     | FileCheck %s --check-prefixes=CHECK-DIS,CHECK-O,CHECK-O2,CHECK-PRELINK-O,CHECK-PRELINK-O2
+; Enabling the hot-cold-split pass should not affect the ThinLTO pre-link
+; RUN: opt -disable-verify -debug-pass-manager \
+; RUN:     -passes='thinlto-pre-link<O2>,name-anon-globals' -hot-cold-split -S  %s 2>&1 \
+; RUN:     | FileCheck %s --check-prefixes=CHECK-O,CHECK-O2,CHECK-PRELINK-O,CHECK-PRELINK-O-NODIS,CHECK-PRELINK-O2
 ;
 ; Postlink pipelines:
 ; RUN: opt -disable-verify -debug-pass-manager \