1 //===- AMDGPUOpenCLEnqueuedBlockLowering.cpp - Lower enqueued block -------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 // This post-linking pass replaces the function pointer of enqueued
12 // block kernel with a global variable (runtime handle) and adds
13 // "runtime-handle" attribute to the enqueued block kernel.
15 // In LLVM CodeGen the runtime-handle metadata will be translated to
16 // RuntimeHandle metadata in code object. Runtime allocates a global buffer
17 // for each kernel with RuntimeHandel metadata and saves the kernel address
18 // required for the AQL packet into the buffer. __enqueue_kernel function
19 // in device library knows that the invoke function pointer in the block
20 // literal is actually runtime handle and loads the kernel address from it
21 // and put it into AQL packet for dispatching.
23 // This cannot be done in FE since FE cannot create a unique global variable
24 // with external linkage across LLVM modules. The global variable with internal
25 // linkage does not work since optimization passes will try to replace loads
26 // of the global variable with its initialization value.
28 // It also identifies the kernels directly or indirectly enqueues kernels
29 // and adds "calls-enqueue-kernel" function attribute to them, which will
30 // be used to determine whether to emit runtime metadata for the kernel
31 // enqueue related hidden kernel arguments.
33 //===----------------------------------------------------------------------===//
36 #include "llvm/ADT/DenseSet.h"
37 #include "llvm/ADT/StringRef.h"
38 #include "llvm/IR/Constants.h"
39 #include "llvm/IR/DerivedTypes.h"
40 #include "llvm/IR/Instructions.h"
41 #include "llvm/IR/Mangler.h"
42 #include "llvm/IR/Module.h"
43 #include "llvm/IR/User.h"
44 #include "llvm/Pass.h"
45 #include "llvm/Support/Debug.h"
46 #include "llvm/Support/raw_ostream.h"
48 #define DEBUG_TYPE "amdgpu-lower-enqueued-block"
54 /// Lower enqueued blocks.
55 class AMDGPUOpenCLEnqueuedBlockLowering : public ModulePass {
59 explicit AMDGPUOpenCLEnqueuedBlockLowering() : ModulePass(ID) {}
62 bool runOnModule(Module &M) override;
65 } // end anonymous namespace
67 char AMDGPUOpenCLEnqueuedBlockLowering::ID = 0;
69 char &llvm::AMDGPUOpenCLEnqueuedBlockLoweringID =
70 AMDGPUOpenCLEnqueuedBlockLowering::ID;
72 INITIALIZE_PASS(AMDGPUOpenCLEnqueuedBlockLowering, DEBUG_TYPE,
73 "Lower OpenCL enqueued blocks", false, false)
75 ModulePass* llvm::createAMDGPUOpenCLEnqueuedBlockLoweringPass() {
76 return new AMDGPUOpenCLEnqueuedBlockLowering();
79 /// Collect direct or indrect callers of \p F and save them
81 static void collectCallers(Function *F, DenseSet<Function *> &Callers) {
82 for (auto U : F->users()) {
83 if (auto *CI = dyn_cast<CallInst>(&*U)) {
84 auto *Caller = CI->getParent()->getParent();
85 if (Callers.insert(Caller).second)
86 collectCallers(Caller, Callers);
91 /// If \p U is instruction or constant, collect functions which directly or
92 /// indirectly use it.
93 static void collectFunctionUsers(User *U, DenseSet<Function *> &Funcs) {
94 if (auto *I = dyn_cast<Instruction>(U)) {
95 auto *F = I->getParent()->getParent();
96 if (Funcs.insert(F).second)
97 collectCallers(F, Funcs);
100 if (!isa<Constant>(U))
102 for (auto UU : U->users())
103 collectFunctionUsers(&*UU, Funcs);
106 bool AMDGPUOpenCLEnqueuedBlockLowering::runOnModule(Module &M) {
107 DenseSet<Function *> Callers;
108 auto &C = M.getContext();
109 bool Changed = false;
110 for (auto &F : M.functions()) {
111 if (F.hasFnAttribute("enqueued-block")) {
113 SmallString<64> Name;
114 Mangler::getNameWithPrefix(Name, "__amdgpu_enqueued_kernel",
118 LLVM_DEBUG(dbgs() << "found enqueued kernel: " << F.getName() << '\n');
119 auto RuntimeHandle = (F.getName() + ".runtime_handle").str();
120 auto T = ArrayType::get(Type::getInt64Ty(C), 2);
121 auto *GV = new GlobalVariable(
123 /*IsConstant=*/false, GlobalValue::ExternalLinkage,
124 /*Initializer=*/Constant::getNullValue(T), RuntimeHandle,
125 /*InsertBefore=*/nullptr, GlobalValue::NotThreadLocal,
126 AMDGPUAS::GLOBAL_ADDRESS,
127 /*IsExternallyInitialized=*/false);
128 LLVM_DEBUG(dbgs() << "runtime handle created: " << *GV << '\n');
130 for (auto U : F.users()) {
132 if (!isa<ConstantExpr>(UU))
134 collectFunctionUsers(UU, Callers);
135 auto *BitCast = cast<ConstantExpr>(UU);
136 auto *NewPtr = ConstantExpr::getPointerCast(GV, BitCast->getType());
137 BitCast->replaceAllUsesWith(NewPtr);
138 F.addFnAttr("runtime-handle", RuntimeHandle);
139 F.setLinkage(GlobalValue::ExternalLinkage);
145 for (auto F : Callers) {
146 if (F->getCallingConv() != CallingConv::AMDGPU_KERNEL)
148 F->addFnAttr("calls-enqueue-kernel");
149 LLVM_DEBUG(dbgs() << "mark enqueue_kernel caller:" << F->getName() << '\n');