[llvm] [AMDGPU] Enable amdgpu-sw-lower-lds pass to lower LDS accesses to use device global memory (PR #87265)

[Matt Arsenault via llvm-commits]

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+//===-- AMDGPUSwLowerLDS.cpp -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass lowers the local data store, LDS, uses in kernel and non-kernel
+// functions in module with dynamically allocated device global memory.
+//
+// Replacement of Kernel LDS accesses:
+//    For a kernel, LDS access can be static or dynamic which are direct
+//    (accessed within kernel) and indirect (accessed through non-kernels).
+//    A device global memory equal to size of all these LDS globals will be
+//    allocated. At the prologue of the kernel, a single work-item from the
+//    work-group, does a "malloc" and stores the pointer of the allocation in
+//    new LDS global that will be created for the kernel. This will be called
+//    "malloc LDS global" in this pass.
+//    Each LDS access corresponds to an offset in the allocated memory.
+//    All static LDS accesses will be allocated first and then dynamic LDS
+//    will occupy the device global memoery.
+//    To store the offsets corresponding to all LDS accesses, another global
+//    variable is created which will be called "metadata global" in this pass.
+//    - Malloc LDS Global:
+//        It is LDS global of ptr type with name
+//        "llvm.amdgcn.sw.lds.<kernel-name>".
+//    - Metadata Global:
+//        It is of struct type, with n members. n equals the number of LDS
+//        globals accessed by the kernel(direct and indirect). Each member of
+//        struct is another struct of type {i32, i32}. First member corresponds
+//        to offset, second member corresponds to size of LDS global being
+//        replaced. It will have name "llvm.amdgcn.sw.lds.<kernel-name>.md".
+//        This global will have an intializer with static LDS related offsets
+//        and sizes initialized. But for dynamic LDS related entries, offsets
+//        will be intialized to previous static LDS allocation end offset. Sizes
+//        for them will be zero initially. These dynamic LDS offset and size
+//        values will be updated with in the kernel, since kernel can read the
+//        dynamic LDS size allocation done at runtime with query to
+//        "hidden_dynamic_lds_size" hidden kernel argument.
+//
+//    LDS accesses within the kernel will be replaced by "gep" ptr to
+//    corresponding offset into allocated device global memory for the kernel.
+//    At the epilogue of kernel, allocated memory would be made free by the same
+//    single work-item.
+//
+// Replacement of non-kernel LDS accesses:
+//    Multiple kernels can access the same non-kernel function.
+//    All the kernels accessing LDS through non-kernels are sorted and
+//    assigned a kernel-id. All the LDS globals accessed by non-kernels
+//    are sorted. This information is used to build two tables:
+//    - Base table:
+//        Base table will have single row, with elements of the row
+//        placed as per kernel ID. Each element in the row corresponds
+//        to addresss of "malloc LDS global" variable created for
+//        that kernel.
+//    - Offset table:
+//        Offset table will have multiple rows and columns.
+//        Rows are assumed to be from 0 to (n-1). n is total number
+//        of kernels accessing the LDS through non-kernels.
+//        Each row will have m elements. m is the total number of
+//        unique LDS globals accessed by all non-kernels.
+//        Each element in the row correspond to the address of
+//        the replacement of LDS global done by that particular kernel.
+//    A LDS variable in non-kernel will be replaced based on the information
+//    from base and offset tables. Based on kernel-id query, address of "malloc
+//    LDS global" for that corresponding kernel is obtained from base table.
+//    The Offset into the base "malloc LDS global" is obtained from
+//    corresponding element in offset table. With this information, replacement
+//    value is obtained.
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "Utils/AMDGPUMemoryUtils.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/SetOperations.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Analysis/CallGraph.h"
+#include "llvm/Analysis/DomTreeUpdater.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicsAMDGPU.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/ReplaceConstant.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+#include <algorithm>
+
+#define DEBUG_TYPE "amdgpu-sw-lower-lds"
+
+using namespace llvm;
+using namespace AMDGPU;
+
+namespace {
+
+using DomTreeCallback = function_ref<DominatorTree *(Function &F)>;
+
+struct LDSAccessTypeInfo {
+  SetVector<GlobalVariable *> StaticLDSGlobals;
+  SetVector<GlobalVariable *> DynamicLDSGlobals;
+};
+
+// Struct to hold all the Metadata required for a kernel
+// to replace a LDS global uses with corresponding offset
+// in to device global memory.
+struct KernelLDSParameters {
+  GlobalVariable *MallocLDSGlobal{nullptr};
+  GlobalVariable *MallocMetadataGlobal{nullptr};
+  LDSAccessTypeInfo DirectAccess;
+  LDSAccessTypeInfo IndirectAccess;
+  DenseMap<GlobalVariable *, SmallVector<uint32_t, 3>>
+      LDSToReplacementIndicesMap;
+  int32_t KernelId{-1};
+  uint32_t MallocSize{0};
+};
+
+// Struct to store infor for creation of offset table
+// for all the non-kernel LDS accesses.
+struct NonKernelLDSParameters {
+  GlobalVariable *LDSBaseTable{nullptr};
+  GlobalVariable *LDSOffsetTable{nullptr};
+  SetVector<Function *> OrderedKernels;
+  SetVector<GlobalVariable *> OrdereLDSGlobals;
+};
+
+class AMDGPUSwLowerLDS {
+public:
+  AMDGPUSwLowerLDS(Module &mod, DomTreeCallback Callback)
+      : M(mod), IRB(M.getContext()), DTCallback(Callback) {}
+  bool Run();
+  void GetUsesOfLDSByNonKernels(CallGraph const &CG,
+                                FunctionVariableMap &functions);
+  SetVector<Function *>
+  GetOrderedIndirectLDSAccessingKernels(SetVector<Function *> &&Kernels);
+  SetVector<GlobalVariable *>
+  GetOrderedNonKernelAllLDSGlobals(SetVector<GlobalVariable *> &&Variables);
+  void PopulateMallocLDSGlobal(Function *Func);
+  void PopulateMallocMetadataGlobal(Function *Func);
+  void PopulateLDSToReplacementIndicesMap(Function *Func);
+  void ReplaceKernelLDSAccesses(Function *Func);
+  void LowerKernelLDSAccesses(Function *Func, DomTreeUpdater &DTU);
+  void BuildNonKernelLDSOffsetTable(
+      std::shared_ptr<NonKernelLDSParameters> &NKLDSParams);
+  void BuildNonKernelLDSBaseTable(
+      std::shared_ptr<NonKernelLDSParameters> &NKLDSParams);
+  Constant *
+  GetAddressesOfVariablesInKernel(Function *Func,
+                                  SetVector<GlobalVariable *> &Variables);
+  void LowerNonKernelLDSAccesses(
+      Function *Func, SetVector<GlobalVariable *> &LDSGlobals,
+      std::shared_ptr<NonKernelLDSParameters> &NKLDSParams);
+
+private:
+  Module &M;
+  IRBuilder<> IRB;
+  DomTreeCallback DTCallback;
+  DenseMap<Function *, std::shared_ptr<KernelLDSParameters>>
----------------
arsenm wrote:

There should be no reason to use shared_ptr here. Just use the raw struct? or unique_ptr? 

https://github.com/llvm/llvm-project/pull/87265