1 //=- WebAssemblyISelLowering.cpp - WebAssembly DAG Lowering Implementation -==//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 ///
10 /// \file
11 /// \brief This file implements the WebAssemblyTargetLowering class.
12 ///
13 //===----------------------------------------------------------------------===//
14 
15 #include "WebAssemblyISelLowering.h"
16 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
17 #include "WebAssemblyMachineFunctionInfo.h"
18 #include "WebAssemblySubtarget.h"
19 #include "WebAssemblyTargetMachine.h"
20 #include "WebAssemblyTargetObjectFile.h"
21 #include "llvm/CodeGen/Analysis.h"
22 #include "llvm/CodeGen/MachineRegisterInfo.h"
23 #include "llvm/CodeGen/SelectionDAG.h"
24 #include "llvm/IR/DiagnosticInfo.h"
25 #include "llvm/IR/DiagnosticPrinter.h"
26 #include "llvm/IR/Function.h"
27 #include "llvm/IR/Intrinsics.h"
28 #include "llvm/Support/CommandLine.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Support/raw_ostream.h"
32 #include "llvm/Target/TargetOptions.h"
33 
34 using namespace llvm;
35 
36 #define DEBUG_TYPE "wasm-lower"
37 
38 namespace {
39 // Diagnostic information for unimplemented or unsupported feature reporting.
40 // FIXME copied from BPF and AMDGPU.
41 class DiagnosticInfoUnsupported : public DiagnosticInfo {
42 private:
43   // Debug location where this diagnostic is triggered.
44   DebugLoc DLoc;
45   const Twine &Description;
46   const Function &Fn;
47   SDValue Value;
48 
49   static int KindID;
50 
51   static int getKindID() {
52     if (KindID == 0)
53       KindID = llvm::getNextAvailablePluginDiagnosticKind();
54     return KindID;
55   }
56 
57 public:
58   DiagnosticInfoUnsupported(SDLoc DLoc, const Function &Fn, const Twine &Desc,
59                             SDValue Value)
60       : DiagnosticInfo(getKindID(), DS_Error), DLoc(DLoc.getDebugLoc()),
61         Description(Desc), Fn(Fn), Value(Value) {}
62 
63   void print(DiagnosticPrinter &DP) const override {
64     std::string Str;
65     raw_string_ostream OS(Str);
66 
67     if (DLoc) {
68       auto DIL = DLoc.get();
69       StringRef Filename = DIL->getFilename();
70       unsigned Line = DIL->getLine();
71       unsigned Column = DIL->getColumn();
72       OS << Filename << ':' << Line << ':' << Column << ' ';
73     }
74 
75     OS << "in function " << Fn.getName() << ' ' << *Fn.getFunctionType() << '\n'
76        << Description;
77     if (Value)
78       Value->print(OS);
79     OS << '\n';
80     OS.flush();
81     DP << Str;
82   }
83 
84   static bool classof(const DiagnosticInfo *DI) {
85     return DI->getKind() == getKindID();
86   }
87 };
88 
89 int DiagnosticInfoUnsupported::KindID = 0;
90 } // end anonymous namespace
91 
92 WebAssemblyTargetLowering::WebAssemblyTargetLowering(
93     const TargetMachine &TM, const WebAssemblySubtarget &STI)
94     : TargetLowering(TM), Subtarget(&STI) {
95   // Booleans always contain 0 or 1.
96   setBooleanContents(ZeroOrOneBooleanContent);
97   // WebAssembly does not produce floating-point exceptions on normal floating
98   // point operations.
99   setHasFloatingPointExceptions(false);
100   // We don't know the microarchitecture here, so just reduce register pressure.
101   setSchedulingPreference(Sched::RegPressure);
102   // Tell ISel that we have a stack pointer.
103   setStackPointerRegisterToSaveRestore(
104       Subtarget->hasAddr64() ? WebAssembly::SP64 : WebAssembly::SP32);
105   // Set up the register classes.
106   addRegisterClass(MVT::i32, &WebAssembly::Int32RegClass);
107   addRegisterClass(MVT::i64, &WebAssembly::Int64RegClass);
108   addRegisterClass(MVT::f32, &WebAssembly::Float32RegClass);
109   addRegisterClass(MVT::f64, &WebAssembly::Float64RegClass);
110   // Compute derived properties from the register classes.
111   computeRegisterProperties(Subtarget->getRegisterInfo());
112 
113   // FIXME: many setOperationAction are missing...
114 
115   for (auto T : {MVT::f32, MVT::f64}) {
116     // Don't expand the floating-point types to constant pools.
117     setOperationAction(ISD::ConstantFP, T, Legal);
118     // Expand floating-point comparisons.
119     for (auto CC : {ISD::SETO, ISD::SETUO, ISD::SETUEQ, ISD::SETONE,
120                     ISD::SETULT, ISD::SETULE, ISD::SETUGT, ISD::SETUGE})
121       setCondCodeAction(CC, T, Expand);
122   }
123 }
124 
125 MVT WebAssemblyTargetLowering::getScalarShiftAmountTy(const DataLayout &DL,
126                                                       EVT VT) const {
127   return VT.getSimpleVT();
128 }
129 
130 const char *
131 WebAssemblyTargetLowering::getTargetNodeName(unsigned Opcode) const {
132   switch (static_cast<WebAssemblyISD::NodeType>(Opcode)) {
133   case WebAssemblyISD::FIRST_NUMBER: break;
134   case WebAssemblyISD::RETURN: return "WebAssemblyISD::RETURN";
135   case WebAssemblyISD::ARGUMENT: return "WebAssemblyISD::ARGUMENT";
136   }
137   return nullptr;
138 }
139 
140 //===----------------------------------------------------------------------===//
141 // WebAssembly Lowering private implementation.
142 //===----------------------------------------------------------------------===//
143 
144 //===----------------------------------------------------------------------===//
145 // Lowering Code
146 //===----------------------------------------------------------------------===//
147 
148 static void fail(SDLoc DL, SelectionDAG &DAG, const char *msg) {
149   MachineFunction &MF = DAG.getMachineFunction();
150   DAG.getContext()->diagnose(
151       DiagnosticInfoUnsupported(DL, *MF.getFunction(), msg, SDValue()));
152 }
153 
154 bool WebAssemblyTargetLowering::CanLowerReturn(
155     CallingConv::ID CallConv, MachineFunction &MF, bool IsVarArg,
156     const SmallVectorImpl<ISD::OutputArg> &Outs, LLVMContext &Context) const {
157   // WebAssembly can't currently handle returning tuples.
158   return Outs.size() <= 1;
159 }
160 
161 SDValue WebAssemblyTargetLowering::LowerReturn(
162     SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
163     const SmallVectorImpl<ISD::OutputArg> &Outs,
164     const SmallVectorImpl<SDValue> &OutVals, SDLoc DL,
165     SelectionDAG &DAG) const {
166 
167   assert(Outs.size() <= 1 && "WebAssembly can only return up to one value");
168   if (CallConv != CallingConv::C)
169     fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
170   if (IsVarArg)
171     fail(DL, DAG, "WebAssembly doesn't support varargs yet");
172 
173   SmallVector<SDValue, 4> RetOps(1, Chain);
174   RetOps.append(OutVals.begin(), OutVals.end());
175   Chain = DAG.getNode(WebAssemblyISD::RETURN, DL, MVT::Other, RetOps);
176 
177   return Chain;
178 }
179 
180 SDValue WebAssemblyTargetLowering::LowerFormalArguments(
181     SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
182     const SmallVectorImpl<ISD::InputArg> &Ins, SDLoc DL, SelectionDAG &DAG,
183     SmallVectorImpl<SDValue> &InVals) const {
184   MachineFunction &MF = DAG.getMachineFunction();
185 
186   if (CallConv != CallingConv::C)
187     fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
188   if (IsVarArg)
189     fail(DL, DAG, "WebAssembly doesn't support varargs yet");
190   if (MF.getFunction()->hasStructRetAttr())
191     fail(DL, DAG, "WebAssembly doesn't support struct return yet");
192 
193   unsigned ArgNo = 0;
194   for (const ISD::InputArg &In : Ins) {
195     if (In.Flags.isZExt())
196       fail(DL, DAG, "WebAssembly hasn't implemented zext arguments");
197     if (In.Flags.isSExt())
198       fail(DL, DAG, "WebAssembly hasn't implemented sext arguments");
199     if (In.Flags.isInReg())
200       fail(DL, DAG, "WebAssembly hasn't implemented inreg arguments");
201     if (In.Flags.isSRet())
202       fail(DL, DAG, "WebAssembly hasn't implemented sret arguments");
203     if (In.Flags.isByVal())
204       fail(DL, DAG, "WebAssembly hasn't implemented byval arguments");
205     if (In.Flags.isInAlloca())
206       fail(DL, DAG, "WebAssembly hasn't implemented inalloca arguments");
207     if (In.Flags.isNest())
208       fail(DL, DAG, "WebAssembly hasn't implemented nest arguments");
209     if (In.Flags.isReturned())
210       fail(DL, DAG, "WebAssembly hasn't implemented returned arguments");
211     if (In.Flags.isInConsecutiveRegs())
212       fail(DL, DAG, "WebAssembly hasn't implemented cons regs arguments");
213     if (In.Flags.isInConsecutiveRegsLast())
214       fail(DL, DAG, "WebAssembly hasn't implemented cons regs last arguments");
215     if (In.Flags.isSplit())
216       fail(DL, DAG, "WebAssembly hasn't implemented split arguments");
217     // FIXME Do something with In.getOrigAlign()?
218     InVals.push_back(
219         In.Used
220             ? DAG.getNode(WebAssemblyISD::ARGUMENT, DL, In.VT,
221                           DAG.getTargetConstant(ArgNo, DL, MVT::i32))
222             : DAG.getNode(ISD::UNDEF, DL, In.VT));
223     ++ArgNo;
224   }
225 
226   return Chain;
227 }
228 
229 //===----------------------------------------------------------------------===//
230 //  Other Lowering Code
231 //===----------------------------------------------------------------------===//
232 
233 //===----------------------------------------------------------------------===//
234 //                          WebAssembly Optimization Hooks
235 //===----------------------------------------------------------------------===//
236 
237 MCSection *WebAssemblyTargetObjectFile::SelectSectionForGlobal(
238     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
239     const TargetMachine &TM) const {
240   return getDataSection();
241 }
242