[MLIR][OpenMP] Remove sinking of loop index allocas

This patch reverts an older patch intended to prevent allocations for loop
index variables from being passed to outlined functions created for the device.

After the transition to the delayed privatization approach, this code is no
longer serving any purpose.

Author: skatrak

mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp

@@ -578,50 +578,6 @@ convertIgnoredWrapper(omp::LoopWrapperInterface opInst,
       });
 }
 
-/// Populate a set of previously created llvm.alloca instructions that are only
-/// used inside of the given region but defined outside of it. Allocations of
-/// non-primitive types are skipped by this function.
-static void getSinkableAllocas(LLVM::ModuleTranslation &moduleTranslation,
-                               Region &region,
-                               SetVector<llvm::AllocaInst *> &allocasToSink) {
-  Operation *op = region.getParentOp();
-
-  for (auto storeOp : region.getOps<LLVM::StoreOp>()) {
-    Value storeAddr = storeOp.getAddr();
-    Operation *addrOp = storeAddr.getDefiningOp();
-
-    // The destination address is already defined in this region or it is not an
-    // llvm.alloca operation, so skip it.
-    if (!isa_and_present<LLVM::AllocaOp>(addrOp) || op->isAncestor(addrOp))
-      continue;
-
-    // Get LLVM value to which the address is mapped. It has to be mapped to the
-    // allocation instruction of a scalar type to be marked as sinkable by this
-    // function.
-    llvm::Value *llvmAddr = moduleTranslation.lookupValue(storeAddr);
-    if (!isa_and_present<llvm::AllocaInst>(llvmAddr))
-      continue;
-
-    auto *llvmAlloca = cast<llvm::AllocaInst>(llvmAddr);
-    if (llvmAlloca->getAllocatedType()->getPrimitiveSizeInBits() == 0)
-      continue;
-
-    // Check that the address is only used inside of the region.
-    bool addressUsedOnlyInternally = true;
-    for (auto &addrUse : storeAddr.getUses()) {
-      if (!op->isAncestor(addrUse.getOwner())) {
-        addressUsedOnlyInternally = false;
-        break;
-      }
-    }
-
-    if (!addressUsedOnlyInternally)
-      continue;
-
-    allocasToSink.insert(llvmAlloca);
-  }
-}
-
 /// Converts an OpenMP 'masked' operation into LLVM IR using OpenMPIRBuilder.
 static LogicalResult
 convertOmpMasked(Operation &opInst, llvm::IRBuilderBase &builder,
@@ -2453,9 +2409,6 @@ convertOmpLoopNest(Operation &opInst, llvm::IRBuilderBase &builder,
   // Set up the source location value for OpenMP runtime.
   llvm::OpenMPIRBuilder::LocationDescription ompLoc(builder);
 
-  SetVector<llvm::AllocaInst *> allocasToSink;
-  getSinkableAllocas(moduleTranslation, loopOp.getRegion(), allocasToSink);
-
   // Generator of the canonical loop body.
   SmallVector<llvm::CanonicalLoopInfo *> loopInfos;
   SmallVector<llvm::OpenMPIRBuilder::InsertPointTy> bodyInsertPoints;
@@ -2473,25 +2426,14 @@ convertOmpLoopNest(Operation &opInst, llvm::IRBuilderBase &builder,
     if (loopInfos.size() != loopOp.getNumLoops() - 1)
       return llvm::Error::success();
 
-    // Convert the body of the loop, adding lifetime markers to allocations that
-    // can be sunk into the new block.
+    // Convert the body of the loop.
     builder.restoreIP(ip);
-    for (auto *alloca : allocasToSink) {
-      unsigned size = alloca->getAllocatedType()->getPrimitiveSizeInBits() / 8;
-      builder.CreateLifetimeStart(alloca, builder.getInt64(size));
-    }
-
     llvm::Expected<llvm::BasicBlock *> regionBlock = convertOmpOpRegions(
         loopOp.getRegion(), "omp.loop_nest.region", builder, moduleTranslation);
     if (!regionBlock)
       return regionBlock.takeError();
 
     builder.SetInsertPoint(*regionBlock, (*regionBlock)->begin());
-
-    for (auto *alloca : allocasToSink) {
-      unsigned size = alloca->getAllocatedType()->getPrimitiveSizeInBits() / 8;
-      builder.CreateLifetimeEnd(alloca, builder.getInt64(size));
-    }
     return llvm::Error::success();
   };