[llvm] [LTO][Pipeline][Coro] Add missing coro pass to O0 post-link thinlto pipeline (PR #159497)

[Weibo He via llvm-commits]

https://github.com/NewSigma updated https://github.com/llvm/llvm-project/pull/159497

>From 11177f6d26c580c1ccf542b0792ede5f3fce8eb8 Mon Sep 17 00:00:00 2001
From: NewSigma <NewSigma at 163.com>
Date: Mon, 15 Sep 2025 16:54:21 +0800
Subject: [PATCH 1/2] [LTO][Pipeline][Coro] Add missing coroutine passes to O0
 post-link ThinLTO pipeline

---
 llvm/lib/Passes/PassBuilderPipelines.cpp | 2 +-
 llvm/test/Other/new-pm-O0-defaults.ll    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 98821bb1408a7..fa818c2f80d2c 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -1820,7 +1820,7 @@ ModulePassManager PassBuilder::buildThinLTODefaultPipeline(
     // with ThinLTO in order to avoid leaving undefined references to dead
     // globals in the object file.
     MPM.addPass(EliminateAvailableExternallyPass());
-    MPM.addPass(GlobalDCEPass());
+    MPM.addPass(buildCoroWrapper(ThinOrFullLTOPhase::ThinLTOPostLink));
     return MPM;
   }
   if (!UseCtxProfile.empty()) {
diff --git a/llvm/test/Other/new-pm-O0-defaults.ll b/llvm/test/Other/new-pm-O0-defaults.ll
index 81d1ee0df2c5b..f2ed83ccc79ca 100644
--- a/llvm/test/Other/new-pm-O0-defaults.ll
+++ b/llvm/test/Other/new-pm-O0-defaults.ll
@@ -45,7 +45,7 @@
 ; CHECK-PRE-LINK-NEXT: Running pass: NameAnonGlobalPass
 ; CHECK-THINLTO: Running pass: LowerTypeTestsPass
 ; CHECK-THINLTO-NEXT: Running pass: EliminateAvailableExternallyPass
-; CHECK-THINLTO-NEXT: Running pass: GlobalDCEPass
+; CHECK-THINLTO-NEXT: Running pass: CoroConditionalWrapper
 ; CHECK-LTO: Running pass: CrossDSOCFIPass on [module]
 ; CHECK-LTO-NEXT: Running pass: WholeProgramDevirtPass
 ; CHECK-LTO-NEXT: Running analysis: InnerAnalysisManagerProxy

>From 11d7c92e9dde2cae38958e3a093a88b766c27a9c Mon Sep 17 00:00:00 2001
From: NewSigma <NewSigma at 163.com>
Date: Mon, 22 Sep 2025 13:44:08 +0800
Subject: [PATCH 2/2] Restore GlobalDCE

---
 llvm/lib/Passes/PassBuilderPipelines.cpp | 3 ++-
 llvm/test/Other/new-pm-O0-defaults.ll    | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index fa818c2f80d2c..5202ada76eb5a 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -1816,11 +1816,12 @@ ModulePassManager PassBuilder::buildThinLTODefaultPipeline(
     // in ICP.
     MPM.addPass(LowerTypeTestsPass(nullptr, nullptr,
                                    lowertypetests::DropTestKind::Assume));
+    MPM.addPass(buildCoroWrapper(ThinOrFullLTOPhase::ThinLTOPostLink));
     // Drop available_externally and unreferenced globals. This is necessary
     // with ThinLTO in order to avoid leaving undefined references to dead
     // globals in the object file.
     MPM.addPass(EliminateAvailableExternallyPass());
-    MPM.addPass(buildCoroWrapper(ThinOrFullLTOPhase::ThinLTOPostLink));
+    MPM.addPass(GlobalDCEPass());
     return MPM;
   }
   if (!UseCtxProfile.empty()) {
diff --git a/llvm/test/Other/new-pm-O0-defaults.ll b/llvm/test/Other/new-pm-O0-defaults.ll
index f2ed83ccc79ca..278a89261691a 100644
--- a/llvm/test/Other/new-pm-O0-defaults.ll
+++ b/llvm/test/Other/new-pm-O0-defaults.ll
@@ -44,8 +44,9 @@
 ; CHECK-PRE-LINK: Running pass: CanonicalizeAliasesPass
 ; CHECK-PRE-LINK-NEXT: Running pass: NameAnonGlobalPass
 ; CHECK-THINLTO: Running pass: LowerTypeTestsPass
-; CHECK-THINLTO-NEXT: Running pass: EliminateAvailableExternallyPass
 ; CHECK-THINLTO-NEXT: Running pass: CoroConditionalWrapper
+; CHECK-THINLTO-NEXT: Running pass: EliminateAvailableExternallyPass
+; CHECK-THINLTO-NEXT: Running pass: GlobalDCEPass
 ; CHECK-LTO: Running pass: CrossDSOCFIPass on [module]
 ; CHECK-LTO-NEXT: Running pass: WholeProgramDevirtPass
 ; CHECK-LTO-NEXT: Running analysis: InnerAnalysisManagerProxy