[TailCallElim] Add tailcall elimination pass to LTO pipelines

LTO provides additional opportunities for tailcall elimination due to
link-time inlining and visibility of nocapture attribute. Testing showed
negligible impact on compilation times.

Differential Revision: https://reviews.llvm.org/D58391

llvm-svn: 356511

2 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index 2baff899010..ba0d6c2bd68 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -1185,6 +1185,10 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level, bool DebugLogging,
   // Break up allocas
   FPM.addPass(SROA());
 
+  // LTO provides additional opportunities for tailcall elimination due to
+  // link-time inlining, and visibility of nocapture attribute.
+  FPM.addPass(TailCallElimPass());
+
   // Run a few AA driver optimizations here and now to cleanup the code.
   MPM.addPass(createModuleToFunctionPassAdaptor(std::move(FPM)));
 
diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index 0505135673b..9e241aa335a 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -896,6 +896,10 @@ void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
   // Break up allocas
   PM.add(createSROAPass());
 
+  // LTO provides additional opportunities for tailcall elimination due to
+  // link-time inlining, and visibility of nocapture attribute.
+  PM.add(createTailCallEliminationPass());
+
   // Run a few AA driven optimizations here and now, to cleanup the code.
   PM.add(createPostOrderFunctionAttrsLegacyPass()); // Add nocapture.
   PM.add(createGlobalsAAWrapperPass()); // IP alias analysis.