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 // \brief 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/Instructions.h"
40 #include "llvm/IR/Module.h"
41 #include "llvm/IR/User.h"
42 #include "llvm/Pass.h"
43 #include "llvm/Support/Debug.h"
44 #include "llvm/Support/raw_ostream.h"
46 #define DEBUG_TYPE "amdgpu-lower-enqueued-block"
52 /// \brief Lower enqueued blocks.
53 class AMDGPUOpenCLEnqueuedBlockLowering : public ModulePass {
57 explicit AMDGPUOpenCLEnqueuedBlockLowering() : ModulePass(ID) {}
60 bool runOnModule(Module &M) override;
63 } // end anonymous namespace
65 char AMDGPUOpenCLEnqueuedBlockLowering::ID = 0;
67 char &llvm::AMDGPUOpenCLEnqueuedBlockLoweringID =
68 AMDGPUOpenCLEnqueuedBlockLowering::ID;
70 INITIALIZE_PASS(AMDGPUOpenCLEnqueuedBlockLowering, DEBUG_TYPE,
71 "Lower OpenCL enqueued blocks", false, false)
73 ModulePass* llvm::createAMDGPUOpenCLEnqueuedBlockLoweringPass() {
74 return new AMDGPUOpenCLEnqueuedBlockLowering();
77 /// Collect direct or indrect callers of \p F and save them
79 static void collectCallers(Function *F, DenseSet<Function *> &Callers) {
80 for (auto U : F->users()) {
81 if (auto *CI = dyn_cast<CallInst>(&*U)) {
82 auto *Caller = CI->getParent()->getParent();
83 if (Callers.count(Caller))
85 Callers.insert(Caller);
86 collectCallers(Caller, Callers);
91 bool AMDGPUOpenCLEnqueuedBlockLowering::runOnModule(Module &M) {
92 DenseSet<Function *> Callers;
93 auto &C = M.getContext();
95 for (auto &F : M.functions()) {
96 if (F.hasFnAttribute("enqueued-block")) {
97 if (!F.hasOneUse() || !F.user_begin()->hasOneUse() ||
98 !isa<ConstantExpr>(*F.user_begin()) ||
99 !isa<ConstantExpr>(*F.user_begin()->user_begin())) {
102 auto *BitCast = cast<ConstantExpr>(*F.user_begin());
103 auto *AddrCast = cast<ConstantExpr>(*BitCast->user_begin());
104 auto RuntimeHandle = (F.getName() + "_runtime_handle").str();
105 auto *GV = new GlobalVariable(
106 M, Type::getInt8Ty(C)->getPointerTo(AMDGPUAS::GLOBAL_ADDRESS),
107 /*IsConstant=*/true, GlobalValue::ExternalLinkage,
108 /*Initializer=*/nullptr, RuntimeHandle, /*InsertBefore=*/nullptr,
109 GlobalValue::NotThreadLocal, AMDGPUAS::GLOBAL_ADDRESS,
110 /*IsExternallyInitialized=*/true);
111 DEBUG(dbgs() << "runtime handle created: " << *GV << '\n');
112 auto *NewPtr = ConstantExpr::getPointerCast(GV, AddrCast->getType());
113 AddrCast->replaceAllUsesWith(NewPtr);
114 F.addFnAttr("runtime-handle", RuntimeHandle);
115 F.setLinkage(GlobalValue::ExternalLinkage);
117 // Collect direct or indirect callers of enqueue_kernel.
118 for (auto U : NewPtr->users()) {
119 if (auto *I = dyn_cast<Instruction>(&*U)) {
120 auto *F = I->getParent()->getParent();
122 collectCallers(F, Callers);
129 for (auto F : Callers) {
130 if (F->getCallingConv() != CallingConv::AMDGPU_KERNEL)
132 F->addFnAttr("calls-enqueue-kernel");