David Gross | 1d93a19 | 2015-03-25 14:59:27 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2015, The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
Jean-Luc Brouillet | a2dd52f | 2017-02-16 20:57:26 -0800 | [diff] [blame] | 17 | #include "RSTransforms.h" |
| 18 | #include "RSUtils.h" |
David Gross | 1d93a19 | 2015-03-25 14:59:27 -0700 | [diff] [blame] | 19 | |
| 20 | #include <llvm/IR/Function.h> |
| 21 | #include <llvm/IR/Instructions.h> |
| 22 | #include <llvm/IR/Metadata.h> |
| 23 | #include <llvm/IR/Module.h> |
| 24 | #include <llvm/IR/Type.h> |
| 25 | #include <llvm/Pass.h> |
| 26 | |
| 27 | namespace { |
| 28 | |
| 29 | /* |
| 30 | * RSInvariantPass - This pass looks for Loads that access |
| 31 | * RsExpandKernelDriverInfo instances (which should never be written by |
| 32 | * a script, only by the driver) and marks them "invariant.load". |
| 33 | * |
| 34 | * There should be only two sources of Loads from such instances: |
| 35 | * - An instance can appear as an argument of type |
| 36 | * "RsExpandKernelDriverInfoPfx*" passed to a .expand function by |
| 37 | * the driver. |
| 38 | * - An instance can appear as an argument of type |
| 39 | * "rs_kernel_context_t*" passed to an API query function by the |
| 40 | * user. |
| 41 | * Only the compiler-generated .expand functions and the API query |
| 42 | * functions can see the fields of RsExpandKernelDriverInfo -- |
| 43 | * rs_kernel_context_t is opaque to user code, so there cannot be any |
| 44 | * Loads from it in user code. |
| 45 | * |
| 46 | * This pass should be run |
| 47 | * - after foreachexp, so that it can see the Loads generated within |
| 48 | * .expand functions |
| 49 | * - before inlining, so that it can recognize API query function |
| 50 | * arguments. |
| 51 | * |
| 52 | * WARNINGS: |
| 53 | * - If user code or APIs can modify RsExpandKernelDriverInfo |
| 54 | * instances, this pass MAY ALLOW ILLEGAL OPTIMIZATION. |
| 55 | * - If this pass runs at a different time, it may be ineffective |
| 56 | * (fail to mark some or all eligible Loads, and thereby cost |
| 57 | * performance). |
| 58 | * - If the names of the data types change, this pass may be |
| 59 | * ineffective. |
| 60 | * - If the patterns by which fields are loaded from |
| 61 | * RsExpandKernelDriverInfo instances change, this pass may be |
| 62 | * ineffective. |
| 63 | */ |
| 64 | class RSInvariantPass : public llvm::FunctionPass { |
| 65 | public: |
| 66 | static char ID; |
| 67 | |
| 68 | RSInvariantPass() : FunctionPass(ID), EmptyMDNode(nullptr) { } |
| 69 | |
| 70 | virtual bool doInitialization(llvm::Module &M) { |
| 71 | EmptyMDNode = llvm::MDNode::get(M.getContext(), llvm::None); |
| 72 | return true; |
| 73 | } |
| 74 | |
| 75 | virtual bool runOnFunction(llvm::Function &F) { |
| 76 | bool Changed = false; |
| 77 | |
| 78 | for (llvm::Value &Arg : F.args()) { |
| 79 | const llvm::Type *ArgType = Arg.getType(); |
| 80 | if (ArgType->isPointerTy()) { |
| 81 | const llvm::Type *ArgPtrDomainType = ArgType->getPointerElementType(); |
Pirama Arumuga Nainar | e8b9f06 | 2015-06-12 14:25:28 -0700 | [diff] [blame] | 82 | if (auto ArgPtrDomainStructType = llvm::dyn_cast<llvm::StructType>(ArgPtrDomainType)) { |
Pirama Arumuga Nainar | 150eef4 | 2015-06-18 16:07:35 -0700 | [diff] [blame] | 83 | if (!ArgPtrDomainStructType->isLiteral()) { |
David Gross | 23c2bfe | 2015-06-22 14:19:00 -0700 | [diff] [blame] | 84 | const llvm::StringRef StructName = getUnsuffixedStructName(ArgPtrDomainStructType); |
Pirama Arumuga Nainar | e8b9f06 | 2015-06-12 14:25:28 -0700 | [diff] [blame] | 85 | if (StructName.equals("struct.rs_kernel_context_t") || StructName.equals("RsExpandKernelDriverInfoPfx")) { |
| 86 | Changed |= markInvariantUserLoads(&Arg); |
| 87 | } |
David Gross | 1d93a19 | 2015-03-25 14:59:27 -0700 | [diff] [blame] | 88 | } |
| 89 | } |
| 90 | } |
| 91 | } |
| 92 | |
| 93 | return Changed; |
| 94 | } |
| 95 | |
| 96 | virtual const char *getPassName() const { |
| 97 | return "Renderscript Invariant Load Annotation"; |
| 98 | } |
| 99 | |
| 100 | private: |
| 101 | |
| 102 | /* |
| 103 | * Follow def->use chains rooted at Value through calculations |
| 104 | * "based on" Value (see the "based on" definition at |
| 105 | * http://llvm.org/docs/LangRef.html#pointer-aliasing-rules). If a |
| 106 | * chain reaches the pointer operand of a Load, mark that Load as |
| 107 | * "invariant.load" -- i.e., it accesses memory which does not |
| 108 | * change. |
| 109 | */ |
| 110 | bool markInvariantUserLoads(llvm::Value *Value) { |
| 111 | bool Changed = false; |
| 112 | for (llvm::Use &Use : Value->uses()) { |
| 113 | llvm::Instruction *Inst = llvm::cast<llvm::Instruction>(Use.getUser()); |
| 114 | |
| 115 | /* |
| 116 | * We only examine a small set of opcodes here, because these |
| 117 | * are the opcodes that currently appear in the patterns of |
| 118 | * interest (foreachexp-generated code, and |
| 119 | * rsGet*(rs_kernel_context_t*) APIs). Other opcodes could be |
| 120 | * added if necessary. |
| 121 | */ |
| 122 | if (auto BitCast = llvm::dyn_cast<llvm::BitCastInst>(Inst)) { |
| 123 | Changed |= markInvariantUserLoads(BitCast); |
| 124 | } else if (auto GetElementPtr = llvm::dyn_cast<llvm::GetElementPtrInst>(Inst)) { |
| 125 | if (Use.get() == GetElementPtr->getPointerOperand()) |
| 126 | Changed |= markInvariantUserLoads(GetElementPtr); |
| 127 | } else if (auto Load = llvm::dyn_cast<llvm::LoadInst>(Inst)) { |
| 128 | if (Use.get() == Load->getPointerOperand()) { |
| 129 | Load->setMetadata("invariant.load", EmptyMDNode); |
| 130 | Changed = true; |
| 131 | } |
| 132 | } |
| 133 | } |
| 134 | return Changed; |
| 135 | } |
| 136 | |
| 137 | // Pointer to empty metadata node used for "invariant.load" marking. |
| 138 | llvm::MDNode *EmptyMDNode; |
| 139 | }; // end RSInvariantPass |
| 140 | |
| 141 | char RSInvariantPass::ID = 0; |
| 142 | llvm::RegisterPass<RSInvariantPass> X("rsinvariant", "RS Invariant Load Pass"); |
| 143 | |
| 144 | } // end anonymous namespace |
| 145 | |
| 146 | namespace bcc { |
| 147 | |
| 148 | llvm::FunctionPass * |
| 149 | createRSInvariantPass() { |
| 150 | return new RSInvariantPass(); |
| 151 | } |
| 152 | |
| 153 | } // end namespace bcc |