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 "TGParser.h"
19 #include "llvm/ADT/StringExtras.h"
20 #include "llvm/Support/CommandLine.h"
21 #include "llvm/Support/FileSystem.h"
22 #include "llvm/Support/MemoryBuffer.h"
23 #include "llvm/Support/ToolOutputFile.h"
24 #include "llvm/TableGen/Error.h"
25 #include "llvm/TableGen/Record.h"
26 #include <algorithm>
27 #include <cstdio>
28 #include <system_error>
29 using namespace llvm;
30 
31 static cl::opt<std::string>
32 OutputFilename("o", cl::desc("Output filename"), cl::value_desc("filename"),
33                cl::init("-"));
34 
35 static cl::opt<std::string>
36 DependFilename("d",
37                cl::desc("Dependency filename"),
38                cl::value_desc("filename"),
39                cl::init(""));
40 
41 static cl::opt<std::string>
42 InputFilename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
43 
44 static cl::list<std::string>
45 IncludeDirs("I", cl::desc("Directory of include files"),
46             cl::value_desc("directory"), cl::Prefix);
47 
48 static cl::list<std::string>
49 MacroNames("D", cl::desc("Name of the macro to be defined"),
50             cl::value_desc("macro name"), cl::Prefix);
51 
52 static cl::opt<bool>
53 WriteIfChanged("write-if-changed", cl::desc("Only write output if it changed"));
54 
55 static int reportError(const char *ProgName, Twine Msg) {
56   errs() << ProgName << ": " << Msg;
57   errs().flush();
58   return 1;
59 }
60 
61 /// Create a dependency file for `-d` option.
62 ///
63 /// This functionality is really only for the benefit of the build system.
64 /// It is similar to GCC's `-M*` family of options.
65 static int createDependencyFile(const TGParser &Parser, const char *argv0) {
66   if (OutputFilename == "-")
67     return reportError(argv0, "the option -d must be used together with -o\n");
68 
69   std::error_code EC;
70   ToolOutputFile DepOut(DependFilename, EC, sys::fs::OF_None);
71   if (EC)
72     return reportError(argv0, "error opening " + DependFilename + ":" +
73                                   EC.message() + "\n");
74   DepOut.os() << OutputFilename << ":";
75   for (const auto &Dep : Parser.getDependencies()) {
76     DepOut.os() << ' ' << Dep;
77   }
78   DepOut.os() << "\n";
79   DepOut.keep();
80   return 0;
81 }
82 
83 int llvm::TableGenMain(const char *argv0, TableGenMainFn *MainFn) {
84   RecordKeeper Records;
85 
86   // Parse the input file.
87   ErrorOr<std::unique_ptr<MemoryBuffer>> FileOrErr =
88       MemoryBuffer::getFileOrSTDIN(InputFilename);
89   if (std::error_code EC = FileOrErr.getError())
90     return reportError(argv0, "Could not open input file '" + InputFilename +
91                                   "': " + EC.message() + "\n");
92 
93   // Tell SrcMgr about this buffer, which is what TGParser will pick up.
94   SrcMgr.AddNewSourceBuffer(std::move(*FileOrErr), SMLoc());
95 
96   // Record the location of the include directory so that the lexer can find
97   // it later.
98   SrcMgr.setIncludeDirs(IncludeDirs);
99 
100   TGParser Parser(SrcMgr, MacroNames, Records);
101 
102   if (Parser.ParseFile())
103     return 1;
104 
105   // Write output to memory.
106   std::string OutString;
107   raw_string_ostream Out(OutString);
108   if (MainFn(Out, Records))
109     return 1;
110 
111   // Always write the depfile, even if the main output hasn't changed.
112   // If it's missing, Ninja considers the output dirty.  If this was below
113   // the early exit below and someone deleted the .inc.d file but not the .inc
114   // file, tablegen would never write the depfile.
115   if (!DependFilename.empty()) {
116     if (int Ret = createDependencyFile(Parser, argv0))
117       return Ret;
118   }
119 
120   if (WriteIfChanged) {
121     // Only updates the real output file if there are any differences.
122     // This prevents recompilation of all the files depending on it if there
123     // aren't any.
124     if (auto ExistingOrErr = MemoryBuffer::getFile(OutputFilename))
125       if (std::move(ExistingOrErr.get())->getBuffer() == Out.str())
126         return 0;
127   }
128 
129   std::error_code EC;
130   ToolOutputFile OutFile(OutputFilename, EC, sys::fs::OF_None);
131   if (EC)
132     return reportError(argv0, "error opening " + OutputFilename + ":" +
133                                   EC.message() + "\n");
134   OutFile.os() << Out.str();
135 
136   if (ErrorsPrinted > 0)
137     return reportError(argv0, Twine(ErrorsPrinted) + " errors.\n");
138 
139   // Declare success.
140   OutFile.keep();
141   return 0;
142 }
143