[llvm] 3890215 - [PassBuilder] Add RelLookupTableConverterPass to LTO (#124053)

[via llvm-commits]

Author: gulfemsavrun
Date: 2025-01-28T15:08:03-08:00
New Revision: 38902153fe66cb7a0685728a5a489dff944b4033

URL: https://github.com/llvm/llvm-project/commit/38902153fe66cb7a0685728a5a489dff944b4033
DIFF: https://github.com/llvm/llvm-project/commit/38902153fe66cb7a0685728a5a489dff944b4033.diff

LOG: [PassBuilder] Add RelLookupTableConverterPass to LTO (#124053)

[PassBuilder] Add RelLookupTableConverterPass to LTO

This patch adds RelLookupTableConverterPass into the LTO
post-link optimization pass pipeline. This optimization
converts lookup tables to relative lookup tables to make
them PIC-friendly, which is already included in the non-LTO
pass pipeline. This patch adds this optimization to the
post-link optimization pipeline to discover more
opportunities in the LTO context.

Added: 
    

Modified: 
    llvm/docs/ReleaseNotes.md
    llvm/lib/Passes/PassBuilderPipelines.cpp
    llvm/test/Other/new-pm-lto-defaults.ll

Removed: 
    


################################################################################
diff  --git a/llvm/docs/ReleaseNotes.md b/llvm/docs/ReleaseNotes.md
index 29bf284617b433..e0acb8f48c5b94 100644
--- a/llvm/docs/ReleaseNotes.md
+++ b/llvm/docs/ReleaseNotes.md
@@ -133,6 +133,8 @@ Changes to TableGen
 Changes to Interprocedural Optimizations
 ----------------------------------------
 
+* Added RelLookupTableConverterPass to LTO post-link pass pipeline.
+
 Changes to the AArch64 Backend
 ------------------------------
 

diff  --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 4ec0fb8fc81ea4..17ff3bd37884b7 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -1594,9 +1594,7 @@ PassBuilder::buildModuleOptimizationPipeline(OptimizationLevel Level,
     MPM.addPass(CGProfilePass(LTOPhase == ThinOrFullLTOPhase::FullLTOPostLink ||
                               LTOPhase == ThinOrFullLTOPhase::ThinLTOPostLink));
 
-  // TODO: Relative look table converter pass caused an issue when full lto is
-  // enabled. See https://reviews.llvm.org/D94355 for more details.
-  // Until the issue fixed, disable this pass during pre-linking phase.
+  // RelLookupTableConverterPass runs later in LTO post-link pipeline.
   if (!LTOPreLink)
     MPM.addPass(RelLookupTableConverterPass());
 
@@ -2121,6 +2119,8 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
   if (PTO.MergeFunctions)
     MPM.addPass(MergeFunctionsPass());
 
+  MPM.addPass(RelLookupTableConverterPass());
+
   if (PTO.CallGraphProfile)
     MPM.addPass(CGProfilePass(/*InLTOPostLink=*/true));
 

diff  --git a/llvm/test/Other/new-pm-lto-defaults.ll b/llvm/test/Other/new-pm-lto-defaults.ll
index f788db1e338a1e..59d9ee24527b64 100644
--- a/llvm/test/Other/new-pm-lto-defaults.ll
+++ b/llvm/test/Other/new-pm-lto-defaults.ll
@@ -146,6 +146,7 @@
 ; CHECK-O23SZ-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O23SZ-NEXT: Running pass: EliminateAvailableExternallyPass
 ; CHECK-O23SZ-NEXT: Running pass: GlobalDCEPass
+; CHECK-O23SZ-NEXT: Running pass: RelLookupTableConverterPass
 ; CHECK-O23SZ-NEXT: Running pass: CGProfilePass
 ; CHECK-EP-NEXT: Running pass: NoOpModulePass
 ; CHECK-O-NEXT: Running pass: AnnotationRemarksPass on foo