1 //===- Main.cpp - Top-Level TableGen implementation -----------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // TableGen is a tool which can be used to build up a description of something,
10 // then invoke one or more "tablegen backends" to emit information about the
11 // description in some predefined format.  In practice, this is used by the LLVM
12 // code generators to automate generation of a code generator through a
13 // high-level description of the target.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/TableGen/Main.h"
18 #include "TGLexer.h"
19 #include "TGParser.h"
20 #include "llvm/ADT/StringRef.h"
21 #include "llvm/ADT/Twine.h"
22 #include "llvm/Support/CommandLine.h"
23 #include "llvm/Support/ErrorOr.h"
24 #include "llvm/Support/FileSystem.h"
25 #include "llvm/Support/MemoryBuffer.h"
26 #include "llvm/Support/SMLoc.h"
27 #include "llvm/Support/SourceMgr.h"
28 #include "llvm/Support/ToolOutputFile.h"
29 #include "llvm/Support/raw_ostream.h"
30 #include "llvm/TableGen/Error.h"
31 #include "llvm/TableGen/Record.h"
32 #include "llvm/TableGen/TableGenBackend.h"
33 #include <memory>
34 #include <string>
35 #include <system_error>
36 #include <utility>
37 #include <vector>
38 using namespace llvm;
39 
40 static cl::opt<std::string>
41 OutputFilename("o", cl::desc("Output filename"), cl::value_desc("filename"),
42                cl::init("-"));
43 
44 static cl::opt<std::string>
45 DependFilename("d",
46                cl::desc("Dependency filename"),
47                cl::value_desc("filename"),
48                cl::init(""));
49 
50 static cl::opt<std::string>
51 InputFilename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
52 
53 static cl::list<std::string>
54 IncludeDirs("I", cl::desc("Directory of include files"),
55             cl::value_desc("directory"), cl::Prefix);
56 
57 static cl::list<std::string>
58 MacroNames("D", cl::desc("Name of the macro to be defined"),
59             cl::value_desc("macro name"), cl::Prefix);
60 
61 static cl::opt<bool>
62 WriteIfChanged("write-if-changed", cl::desc("Only write output if it changed"));
63 
64 static cl::opt<bool>
65 TimePhases("time-phases", cl::desc("Time phases of parser and backend"));
66 
67 static cl::opt<bool> NoWarnOnUnusedTemplateArgs(
68     "no-warn-on-unused-template-args",
69     cl::desc("Disable unused template argument warnings."));
70 
71 static int reportError(const char *ProgName, Twine Msg) {
72   errs() << ProgName << ": " << Msg;
73   errs().flush();
74   return 1;
75 }
76 
77 /// Create a dependency file for `-d` option.
78 ///
79 /// This functionality is really only for the benefit of the build system.
80 /// It is similar to GCC's `-M*` family of options.
81 static int createDependencyFile(const TGParser &Parser, const char *argv0) {
82   if (OutputFilename == "-")
83     return reportError(argv0, "the option -d must be used together with -o\n");
84 
85   std::error_code EC;
86   ToolOutputFile DepOut(DependFilename, EC, sys::fs::OF_Text);
87   if (EC)
88     return reportError(argv0, "error opening " + DependFilename + ":" +
89                                   EC.message() + "\n");
90   DepOut.os() << OutputFilename << ":";
91   for (const auto &Dep : Parser.getDependencies()) {
92     DepOut.os() << ' ' << Dep;
93   }
94   DepOut.os() << "\n";
95   DepOut.keep();
96   return 0;
97 }
98 
99 int llvm::TableGenMain(const char *argv0,
100                        std::function<TableGenMainFn> MainFn) {
101   RecordKeeper Records;
102 
103   if (TimePhases)
104     Records.startPhaseTiming();
105 
106   // Parse the input file.
107 
108   Records.startTimer("Parse, build records");
109   ErrorOr<std::unique_ptr<MemoryBuffer>> FileOrErr =
110       MemoryBuffer::getFileOrSTDIN(InputFilename, /*IsText=*/true);
111   if (std::error_code EC = FileOrErr.getError())
112     return reportError(argv0, "Could not open input file '" + InputFilename +
113                                   "': " + EC.message() + "\n");
114 
115   Records.saveInputFilename(InputFilename);
116 
117   // Tell SrcMgr about this buffer, which is what TGParser will pick up.
118   SrcMgr.AddNewSourceBuffer(std::move(*FileOrErr), SMLoc());
119 
120   // Record the location of the include directory so that the lexer can find
121   // it later.
122   SrcMgr.setIncludeDirs(IncludeDirs);
123 
124   TGParser Parser(SrcMgr, MacroNames, Records, NoWarnOnUnusedTemplateArgs);
125 
126   if (Parser.ParseFile())
127     return 1;
128   Records.stopTimer();
129 
130   // Write output to memory.
131   Records.startBackendTimer("Backend overall");
132   std::string OutString;
133   raw_string_ostream Out(OutString);
134   unsigned status = 0;
135   TableGen::Emitter::FnT ActionFn = TableGen::Emitter::Action->getValue();
136   if (ActionFn)
137     ActionFn(Records, Out);
138   else if (MainFn)
139     status = MainFn(Out, Records);
140   else
141     return 1;
142   Records.stopBackendTimer();
143   if (status)
144     return 1;
145 
146   // Always write the depfile, even if the main output hasn't changed.
147   // If it's missing, Ninja considers the output dirty.  If this was below
148   // the early exit below and someone deleted the .inc.d file but not the .inc
149   // file, tablegen would never write the depfile.
150   if (!DependFilename.empty()) {
151     if (int Ret = createDependencyFile(Parser, argv0))
152       return Ret;
153   }
154 
155   Records.startTimer("Write output");
156   bool WriteFile = true;
157   if (WriteIfChanged) {
158     // Only updates the real output file if there are any differences.
159     // This prevents recompilation of all the files depending on it if there
160     // aren't any.
161     if (auto ExistingOrErr =
162             MemoryBuffer::getFile(OutputFilename, /*IsText=*/true))
163       if (std::move(ExistingOrErr.get())->getBuffer() == Out.str())
164         WriteFile = false;
165   }
166   if (WriteFile) {
167     std::error_code EC;
168     ToolOutputFile OutFile(OutputFilename, EC, sys::fs::OF_Text);
169     if (EC)
170       return reportError(argv0, "error opening " + OutputFilename + ": " +
171                                     EC.message() + "\n");
172     OutFile.os() << Out.str();
173     if (ErrorsPrinted == 0)
174       OutFile.keep();
175   }
176 
177   Records.stopTimer();
178   Records.stopPhaseTiming();
179 
180   if (ErrorsPrinted > 0)
181     return reportError(argv0, Twine(ErrorsPrinted) + " errors.\n");
182   return 0;
183 }
184