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   // WebAssembly does not produce floating-point exceptions on normal floating
96   // point operations.
97   setHasFloatingPointExceptions(false);
98   // We don't know the microarchitecture here, so just reduce register pressure.
99   setSchedulingPreference(Sched::RegPressure);
100   // Tell ISel that we have a stack pointer.
101   setStackPointerRegisterToSaveRestore(
102       Subtarget->hasAddr64() ? WebAssembly::SP64 : WebAssembly::SP32);
103   // Set up the register classes.
104   addRegisterClass(MVT::i32, &WebAssembly::Int32RegClass);
105   addRegisterClass(MVT::i64, &WebAssembly::Int64RegClass);
106   addRegisterClass(MVT::f32, &WebAssembly::Float32RegClass);
107   addRegisterClass(MVT::f64, &WebAssembly::Float64RegClass);
108   // Compute derived properties from the register classes.
109   computeRegisterProperties(Subtarget->getRegisterInfo());
110 
111   // FIXME: setOperationAction...
112 }
113 
114 //===----------------------------------------------------------------------===//
115 // WebAssembly Lowering private implementation.
116 //===----------------------------------------------------------------------===//
117 
118 //===----------------------------------------------------------------------===//
119 // Lowering Code
120 //===----------------------------------------------------------------------===//
121 
122 static void fail(SDLoc DL, SelectionDAG &DAG, const char *msg) {
123   MachineFunction &MF = DAG.getMachineFunction();
124   DAG.getContext()->diagnose(
125       DiagnosticInfoUnsupported(DL, *MF.getFunction(), msg, SDValue()));
126 }
127 
128 bool WebAssemblyTargetLowering::CanLowerReturn(
129     CallingConv::ID CallConv, MachineFunction &MF, bool IsVarArg,
130     const SmallVectorImpl<ISD::OutputArg> &Outs, LLVMContext &Context) const {
131   // WebAssembly can't currently handle returning tuples.
132   return Outs.size() <= 1;
133 }
134 
135 SDValue WebAssemblyTargetLowering::LowerReturn(
136     SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
137     const SmallVectorImpl<ISD::OutputArg> &Outs,
138     const SmallVectorImpl<SDValue> &OutVals, SDLoc DL,
139     SelectionDAG &DAG) const {
140 
141   assert(Outs.size() <= 1 && "WebAssembly can only return up to one value");
142   if (CallConv != CallingConv::C)
143     fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
144 
145   // FIXME: Implement LowerReturn.
146 
147   return Chain;
148 }
149 
150 SDValue WebAssemblyTargetLowering::LowerFormalArguments(
151     SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
152     const SmallVectorImpl<ISD::InputArg> &Ins, SDLoc DL, SelectionDAG &DAG,
153     SmallVectorImpl<SDValue> &InVals) const {
154   MachineFunction &MF = DAG.getMachineFunction();
155 
156   if (CallConv != CallingConv::C)
157     fail(DL, DAG, "WebAssembly doesn't support non-C calling conventions");
158   if (IsVarArg)
159     fail(DL, DAG, "WebAssembly doesn't support varargs yet");
160   if (MF.getFunction()->hasStructRetAttr())
161     fail(DL, DAG, "WebAssembly doesn't support struct return yet");
162 
163   // FIXME: Implement LowerFormalArguments.
164   for (const ISD::InputArg &In : Ins)
165     InVals.push_back(DAG.getNode(ISD::UNDEF, DL, In.VT));
166 
167   return Chain;
168 }
169 
170 //===----------------------------------------------------------------------===//
171 //  Other Lowering Code
172 //===----------------------------------------------------------------------===//
173 
174 //===----------------------------------------------------------------------===//
175 //                          WebAssembly Optimization Hooks
176 //===----------------------------------------------------------------------===//
177 
178 MCSection *WebAssemblyTargetObjectFile::SelectSectionForGlobal(
179     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
180     const TargetMachine &TM) const {
181   return getDataSection();
182 }
183