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/Support/CommandLine.h"
20 #include "llvm/Support/FileSystem.h"
21 #include "llvm/Support/MemoryBuffer.h"
22 #include "llvm/Support/ToolOutputFile.h"
23 #include "llvm/TableGen/Error.h"
24 #include "llvm/TableGen/Record.h"
25 #include <algorithm>
26 #include <system_error>
27 using namespace llvm;
28 
29 static cl::opt<std::string>
30 OutputFilename("o", cl::desc("Output filename"), cl::value_desc("filename"),
31                cl::init("-"));
32 
33 static cl::opt<std::string>
34 DependFilename("d",
35                cl::desc("Dependency filename"),
36                cl::value_desc("filename"),
37                cl::init(""));
38 
39 static cl::opt<std::string>
40 InputFilename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
41 
42 static cl::list<std::string>
43 IncludeDirs("I", cl::desc("Directory of include files"),
44             cl::value_desc("directory"), cl::Prefix);
45 
46 static cl::list<std::string>
47 MacroNames("D", cl::desc("Name of the macro to be defined"),
48             cl::value_desc("macro name"), cl::Prefix);
49 
50 static cl::opt<bool>
51 WriteIfChanged("write-if-changed", cl::desc("Only write output if it changed"));
52 
53 static cl::opt<bool>
54 TimePhases("time-phases", cl::desc("Time phases of parser and backend"));
55 
56 static cl::opt<bool> NoWarnOnUnusedTemplateArgs(
57     "no-warn-on-unused-template-args",
58     cl::desc("Disable unused template argument warnings."));
59 
60 static int reportError(const char *ProgName, Twine Msg) {
61   errs() << ProgName << ": " << Msg;
62   errs().flush();
63   return 1;
64 }
65 
66 /// Create a dependency file for `-d` option.
67 ///
68 /// This functionality is really only for the benefit of the build system.
69 /// It is similar to GCC's `-M*` family of options.
70 static int createDependencyFile(const TGParser &Parser, const char *argv0) {
71   if (OutputFilename == "-")
72     return reportError(argv0, "the option -d must be used together with -o\n");
73 
74   std::error_code EC;
75   ToolOutputFile DepOut(DependFilename, EC, sys::fs::OF_Text);
76   if (EC)
77     return reportError(argv0, "error opening " + DependFilename + ":" +
78                                   EC.message() + "\n");
79   DepOut.os() << OutputFilename << ":";
80   for (const auto &Dep : Parser.getDependencies()) {
81     DepOut.os() << ' ' << Dep;
82   }
83   DepOut.os() << "\n";
84   DepOut.keep();
85   return 0;
86 }
87 
88 int llvm::TableGenMain(const char *argv0, TableGenMainFn *MainFn) {
89   RecordKeeper Records;
90 
91   if (TimePhases)
92     Records.startPhaseTiming();
93 
94   // Parse the input file.
95 
96   Records.startTimer("Parse, build records");
97   ErrorOr<std::unique_ptr<MemoryBuffer>> FileOrErr =
98       MemoryBuffer::getFileOrSTDIN(InputFilename, /*IsText=*/true);
99   if (std::error_code EC = FileOrErr.getError())
100     return reportError(argv0, "Could not open input file '" + InputFilename +
101                                   "': " + EC.message() + "\n");
102 
103   Records.saveInputFilename(InputFilename);
104 
105   // Tell SrcMgr about this buffer, which is what TGParser will pick up.
106   SrcMgr.AddNewSourceBuffer(std::move(*FileOrErr), SMLoc());
107 
108   // Record the location of the include directory so that the lexer can find
109   // it later.
110   SrcMgr.setIncludeDirs(IncludeDirs);
111 
112   TGParser Parser(SrcMgr, MacroNames, Records, NoWarnOnUnusedTemplateArgs);
113 
114   if (Parser.ParseFile())
115     return 1;
116   Records.stopTimer();
117 
118   // Write output to memory.
119   Records.startBackendTimer("Backend overall");
120   std::string OutString;
121   raw_string_ostream Out(OutString);
122   unsigned status = MainFn(Out, Records);
123   Records.stopBackendTimer();
124   if (status)
125     return 1;
126 
127   // Always write the depfile, even if the main output hasn't changed.
128   // If it's missing, Ninja considers the output dirty.  If this was below
129   // the early exit below and someone deleted the .inc.d file but not the .inc
130   // file, tablegen would never write the depfile.
131   if (!DependFilename.empty()) {
132     if (int Ret = createDependencyFile(Parser, argv0))
133       return Ret;
134   }
135 
136   Records.startTimer("Write output");
137   bool WriteFile = true;
138   if (WriteIfChanged) {
139     // Only updates the real output file if there are any differences.
140     // This prevents recompilation of all the files depending on it if there
141     // aren't any.
142     if (auto ExistingOrErr =
143             MemoryBuffer::getFile(OutputFilename, /*IsText=*/true))
144       if (std::move(ExistingOrErr.get())->getBuffer() == Out.str())
145         WriteFile = false;
146   }
147   if (WriteFile) {
148     std::error_code EC;
149     ToolOutputFile OutFile(OutputFilename, EC, sys::fs::OF_Text);
150     if (EC)
151       return reportError(argv0, "error opening " + OutputFilename + ": " +
152                                     EC.message() + "\n");
153     OutFile.os() << Out.str();
154     if (ErrorsPrinted == 0)
155       OutFile.keep();
156   }
157 
158   Records.stopTimer();
159   Records.stopPhaseTiming();
160 
161   if (ErrorsPrinted > 0)
162     return reportError(argv0, Twine(ErrorsPrinted) + " errors.\n");
163   return 0;
164 }
165