[llvm-branch-commits] [llvm] [AMDGPU] Remove named-barrier LDS lowering logic from amdgpu-lower-module-lds (PR #166731)

[via llvm-branch-commits]

https://github.com/skc7 created https://github.com/llvm/llvm-project/pull/166731

This PR removes the named-barrier LDS lowering from `amdgpu-lower-module-lds` pass, since it is now handled by `amdgpu-lower-exec-sync` pass

>From 0a2e9ee17ea82a7cb3fe191626ee84b05c37be83 Mon Sep 17 00:00:00 2001
From: skc7 <Krishna.Sankisa at amd.com>
Date: Thu, 6 Nov 2025 14:29:17 +0530
Subject: [PATCH] [AMDGPU] Remove lowering named-barrier LDS logci from
 amdgpu-lower-module-lds

---
 .../AMDGPU/AMDGPULowerModuleLDSPass.cpp       | 126 ------------------
 1 file changed, 126 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/AMDGPULowerModuleLDSPass.cpp b/llvm/lib/Target/AMDGPU/AMDGPULowerModuleLDSPass.cpp
index a4ef524c43466..3c0328e93ffbd 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPULowerModuleLDSPass.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPULowerModuleLDSPass.cpp
@@ -922,126 +922,6 @@ class AMDGPULowerModuleLDS {
     return KernelToCreatedDynamicLDS;
   }
 
-  static GlobalVariable *uniquifyGVPerKernel(Module &M, GlobalVariable *GV,
-                                             Function *KF) {
-    bool NeedsReplacement = false;
-    for (Use &U : GV->uses()) {
-      if (auto *I = dyn_cast<Instruction>(U.getUser())) {
-        Function *F = I->getFunction();
-        if (isKernelLDS(F) && F != KF) {
-          NeedsReplacement = true;
-          break;
-        }
-      }
-    }
-    if (!NeedsReplacement)
-      return GV;
-    // Create a new GV used only by this kernel and its function
-    GlobalVariable *NewGV = new GlobalVariable(
-        M, GV->getValueType(), GV->isConstant(), GV->getLinkage(),
-        GV->getInitializer(), GV->getName() + "." + KF->getName(), nullptr,
-        GV->getThreadLocalMode(), GV->getType()->getAddressSpace());
-    NewGV->copyAttributesFrom(GV);
-    for (Use &U : make_early_inc_range(GV->uses())) {
-      if (auto *I = dyn_cast<Instruction>(U.getUser())) {
-        Function *F = I->getFunction();
-        if (!isKernelLDS(F) || F == KF) {
-          U.getUser()->replaceUsesOfWith(GV, NewGV);
-        }
-      }
-    }
-    return NewGV;
-  }
-
-  bool lowerSpecialLDSVariables(
-      Module &M, LDSUsesInfoTy &LDSUsesInfo,
-      VariableFunctionMap &LDSToKernelsThatNeedToAccessItIndirectly) {
-    bool Changed = false;
-    const DataLayout &DL = M.getDataLayout();
-    // The 1st round: give module-absolute assignments
-    int NumAbsolutes = 0;
-    std::vector<GlobalVariable *> OrderedGVs;
-    for (auto &K : LDSToKernelsThatNeedToAccessItIndirectly) {
-      GlobalVariable *GV = K.first;
-      if (!isNamedBarrier(*GV))
-        continue;
-      // give a module-absolute assignment if it is indirectly accessed by
-      // multiple kernels. This is not precise, but we don't want to duplicate
-      // a function when it is called by multiple kernels.
-      if (LDSToKernelsThatNeedToAccessItIndirectly[GV].size() > 1) {
-        OrderedGVs.push_back(GV);
-      } else {
-        // leave it to the 2nd round, which will give a kernel-relative
-        // assignment if it is only indirectly accessed by one kernel
-        LDSUsesInfo.direct_access[*K.second.begin()].insert(GV);
-      }
-      LDSToKernelsThatNeedToAccessItIndirectly.erase(GV);
-    }
-    OrderedGVs = sortByName(std::move(OrderedGVs));
-    for (GlobalVariable *GV : OrderedGVs) {
-      unsigned BarrierScope = llvm::AMDGPU::Barrier::BARRIER_SCOPE_WORKGROUP;
-      unsigned BarId = NumAbsolutes + 1;
-      unsigned BarCnt = DL.getTypeAllocSize(GV->getValueType()) / 16;
-      NumAbsolutes += BarCnt;
-
-      // 4 bits for alignment, 5 bits for the barrier num,
-      // 3 bits for the barrier scope
-      unsigned Offset = 0x802000u | BarrierScope << 9 | BarId << 4;
-      recordLDSAbsoluteAddress(&M, GV, Offset);
-    }
-    OrderedGVs.clear();
-
-    // The 2nd round: give a kernel-relative assignment for GV that
-    // either only indirectly accessed by single kernel or only directly
-    // accessed by multiple kernels.
-    std::vector<Function *> OrderedKernels;
-    for (auto &K : LDSUsesInfo.direct_access) {
-      Function *F = K.first;
-      assert(isKernelLDS(F));
-      OrderedKernels.push_back(F);
-    }
-    OrderedKernels = sortByName(std::move(OrderedKernels));
-
-    llvm::DenseMap<Function *, uint32_t> Kernel2BarId;
-    for (Function *F : OrderedKernels) {
-      for (GlobalVariable *GV : LDSUsesInfo.direct_access[F]) {
-        if (!isNamedBarrier(*GV))
-          continue;
-
-        LDSUsesInfo.direct_access[F].erase(GV);
-        if (GV->isAbsoluteSymbolRef()) {
-          // already assigned
-          continue;
-        }
-        OrderedGVs.push_back(GV);
-      }
-      OrderedGVs = sortByName(std::move(OrderedGVs));
-      for (GlobalVariable *GV : OrderedGVs) {
-        // GV could also be used directly by other kernels. If so, we need to
-        // create a new GV used only by this kernel and its function.
-        auto NewGV = uniquifyGVPerKernel(M, GV, F);
-        Changed |= (NewGV != GV);
-        unsigned BarrierScope = llvm::AMDGPU::Barrier::BARRIER_SCOPE_WORKGROUP;
-        unsigned BarId = Kernel2BarId[F];
-        BarId += NumAbsolutes + 1;
-        unsigned BarCnt = DL.getTypeAllocSize(GV->getValueType()) / 16;
-        Kernel2BarId[F] += BarCnt;
-        unsigned Offset = 0x802000u | BarrierScope << 9 | BarId << 4;
-        recordLDSAbsoluteAddress(&M, NewGV, Offset);
-      }
-      OrderedGVs.clear();
-    }
-    // Also erase those special LDS variables from indirect_access.
-    for (auto &K : LDSUsesInfo.indirect_access) {
-      assert(isKernelLDS(K.first));
-      for (GlobalVariable *GV : K.second) {
-        if (isNamedBarrier(*GV))
-          K.second.erase(GV);
-      }
-    }
-    return Changed;
-  }
-
   bool runOnModule(Module &M) {
     CallGraph CG = CallGraph(M);
     bool Changed = superAlignLDSGlobals(M);
@@ -1064,12 +944,6 @@ class AMDGPULowerModuleLDS {
       }
     }
 
-    if (LDSUsesInfo.HasSpecialGVs) {
-      // Special LDS variables need special address assignment
-      Changed |= lowerSpecialLDSVariables(
-          M, LDSUsesInfo, LDSToKernelsThatNeedToAccessItIndirectly);
-    }
-
     // Partition variables accessed indirectly into the different strategies
     DenseSet<GlobalVariable *> ModuleScopeVariables;
     DenseSet<GlobalVariable *> TableLookupVariables;