From 98cae0e8835a1eb8fcb0e43870c04ed934cc51ac Mon Sep 17 00:00:00 2001
From: Richard-Qin-X <richard.qin.001@gmail.com>
Date: Thu, 13 Aug 2026 19:38:37 +0800
Subject: [CodeGen] Match LLVM branch relaxation semantics

---
 backend/lib/CodeGen/MachineBranchRelaxation.cpp | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

(limited to 'backend/lib/CodeGen/MachineBranchRelaxation.cpp')

diff --git a/backend/lib/CodeGen/MachineBranchRelaxation.cpp b/backend/lib/CodeGen/MachineBranchRelaxation.cpp
index 9f14fc4..4df4cc8 100644
--- a/backend/lib/CodeGen/MachineBranchRelaxation.cpp
+++ b/backend/lib/CodeGen/MachineBranchRelaxation.cpp
@@ -2,7 +2,6 @@
 
 #include "rcc/CodeGen/MachineBranchRelaxation.h"
 
-#include "rcc/CodeGen/LiveVariables.h"
 #include "rcc/CodeGen/MachineBasicBlock.h"
 #include "rcc/CodeGen/MachineFunction.h"
 #include "rcc/CodeGen/MachineFunctionCloner.h"
@@ -29,16 +28,12 @@ struct MachineLayout final {
 [[nodiscard]] const MachinePassContract &relaxationContract() {
   static const MachinePassContract Contract = [] {
     MachinePassContract Value{
-        .Name = "machine-branch-relaxation",
-        .Requires = {MachineFunctionProperty::Selected, MachineFunctionProperty::NoPHIs,
-                     MachineFunctionProperty::TiedOpsRewritten, MachineFunctionProperty::NoVRegs,
-                     MachineFunctionProperty::TracksLiveness,
-                     MachineFunctionProperty::FrameFinalized,
-                     MachineFunctionProperty::NoFrameIndices},
+        .Name = "branch-relaxation",
+        .Requires = {MachineFunctionProperty::TracksLiveness},
         .Sets = {},
         .Clears = {},
         .RequiredAnalyses = {},
-        .VerificationStage = PipelineStage::PostRAFinalized,
+        .VerificationStage = std::nullopt,
     };
     Value.ThreadSafety = PassThreadSafety::ThreadSafe;
     Value.DeclaredChanges = {MachinePassChange::Instructions, MachinePassChange::Operands};
@@ -107,7 +102,7 @@ MachineBranchRelaxationPass::run(MachineFunction &Function, const TargetDescript
                                  MachineFunctionAnalysisManager &Analyses) {
   if (!Function.properties().containsAll(contract().Requires)) {
     return makeUnexpected(ErrorCode::VerificationError,
-                          "branch relaxation requires finalized frame and tracked liveness");
+                          "branch relaxation requires tracked liveness");
   }
   auto Trial = cloneMachineFunction(
       Function, Target,
@@ -185,9 +180,6 @@ MachineBranchRelaxationPass::runImplementation(MachineFunction &Function,
     if (Changed)
       continue;
     if (Result.Changed) {
-      auto Rebuilt = rebuildMachineLiveness(Function, Target);
-      if (!Rebuilt)
-        return std::unexpected(Rebuilt.error());
       Result.Changes = {MachinePassChange::Instructions, MachinePassChange::Operands};
       Result.Preserved = PreservedAnalyses::none();
     } else {
-- 
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