Imported Upstream version 6.0.0.172

Former-commit-id: f3cc9b82f3e5bd8f0fd3ebc098f789556b44e9cd

external/llvm/lib/Target/AMDGPU/AMDGPUOpenCLEnqueuedBlockLowering.cpp

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+//===- AMDGPUOpenCLEnqueuedBlockLowering.cpp - Lower enqueued block -------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// \file
+// \brief This post-linking pass replaces the function pointer of enqueued
+// block kernel with a global variable (runtime handle) and adds
+// "runtime-handle" attribute to the enqueued block kernel.
+//
+// In LLVM CodeGen the runtime-handle metadata will be translated to
+// RuntimeHandle metadata in code object. Runtime allocates a global buffer
+// for each kernel with RuntimeHandel metadata and saves the kernel address
+// required for the AQL packet into the buffer. __enqueue_kernel function
+// in device library knows that the invoke function pointer in the block
+// literal is actually runtime handle and loads the kernel address from it
+// and put it into AQL packet for dispatching.
+//
+// This cannot be done in FE since FE cannot create a unique global variable
+// with external linkage across LLVM modules. The global variable with internal
+// linkage does not work since optimization passes will try to replace loads
+// of the global variable with its initialization value.
+//
+// It also identifies the kernels directly or indirectly enqueues kernels
+// and adds "calls-enqueue-kernel" function attribute to them, which will
+// be used to determine whether to emit runtime metadata for the kernel
+// enqueue related hidden kernel arguments.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/User.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+
+#define DEBUG_TYPE "amdgpu-lower-enqueued-block"
+
+using namespace llvm;
+
+namespace {
+
+/// \brief Lower enqueued blocks.
+class AMDGPUOpenCLEnqueuedBlockLowering : public ModulePass {
+public:
+  static char ID;
+
+  explicit AMDGPUOpenCLEnqueuedBlockLowering() : ModulePass(ID) {}
+
+private:
+  bool runOnModule(Module &M) override;
+};
+
+} // end anonymous namespace
+
+char AMDGPUOpenCLEnqueuedBlockLowering::ID = 0;
+
+char &llvm::AMDGPUOpenCLEnqueuedBlockLoweringID =
+    AMDGPUOpenCLEnqueuedBlockLowering::ID;
+
+INITIALIZE_PASS(AMDGPUOpenCLEnqueuedBlockLowering, DEBUG_TYPE,
+                "Lower OpenCL enqueued blocks", false, false)
+
+ModulePass* llvm::createAMDGPUOpenCLEnqueuedBlockLoweringPass() {
+  return new AMDGPUOpenCLEnqueuedBlockLowering();
+}
+
+/// Collect direct or indrect callers of \p F and save them
+/// to \p Callers.
+static void collectCallers(Function *F, DenseSet<Function *> &Callers) {
+  for (auto U : F->users()) {
+    if (auto *CI = dyn_cast<CallInst>(&*U)) {
+      auto *Caller = CI->getParent()->getParent();
+      if (Callers.count(Caller))
+        continue;
+      Callers.insert(Caller);
+      collectCallers(Caller, Callers);
+    }
+  }
+}
+
+bool AMDGPUOpenCLEnqueuedBlockLowering::runOnModule(Module &M) {
+  DenseSet<Function *> Callers;
+  auto &C = M.getContext();
+  bool Changed = false;
+  for (auto &F : M.functions()) {
+    if (F.hasFnAttribute("enqueued-block")) {
+      if (!F.hasOneUse() || !F.user_begin()->hasOneUse() ||
+          !isa<ConstantExpr>(*F.user_begin()) ||
+          !isa<ConstantExpr>(*F.user_begin()->user_begin())) {
+        continue;
+      }
+      auto *BitCast = cast<ConstantExpr>(*F.user_begin());
+      auto *AddrCast = cast<ConstantExpr>(*BitCast->user_begin());
+      auto RuntimeHandle = (F.getName() + "_runtime_handle").str();
+      auto *GV = new GlobalVariable(
+          M, Type::getInt8Ty(C)->getPointerTo(AMDGPUAS::GLOBAL_ADDRESS),
+          /*IsConstant=*/true, GlobalValue::ExternalLinkage,
+          /*Initializer=*/nullptr, RuntimeHandle, /*InsertBefore=*/nullptr,
+          GlobalValue::NotThreadLocal, AMDGPUAS::GLOBAL_ADDRESS,
+          /*IsExternallyInitialized=*/true);
+      DEBUG(dbgs() << "runtime handle created: " << *GV << '\n');
+      auto *NewPtr = ConstantExpr::getPointerCast(GV, AddrCast->getType());
+      AddrCast->replaceAllUsesWith(NewPtr);
+      F.addFnAttr("runtime-handle", RuntimeHandle);
+      F.setLinkage(GlobalValue::ExternalLinkage);
+
+      // Collect direct or indirect callers of enqueue_kernel.
+      for (auto U : NewPtr->users()) {
+        if (auto *I = dyn_cast<Instruction>(&*U)) {
+          auto *F = I->getParent()->getParent();
+          Callers.insert(F);
+          collectCallers(F, Callers);
+        }
+      }
+      Changed = true;
+    }
+  }
+
+  for (auto F : Callers) {
+    if (F->getCallingConv() != CallingConv::AMDGPU_KERNEL)
+      continue;
+    F->addFnAttr("calls-enqueue-kernel");
+  }
+  return Changed;
+}