1 //===--- llvm-as.cpp - The low-level LLVM assembler -----------------------===//
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 //  This utility may be invoked in the following manner:
10 //   llvm-as --help         - Output information about command line switches
11 //   llvm-as [options]      - Read LLVM asm from stdin, write bitcode to stdout
12 //   llvm-as [options] x.ll - Read LLVM asm from the x.ll file, write bitcode
13 //                            to the x.bc file.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/AsmParser/Parser.h"
18 #include "llvm/Bitcode/BitcodeWriter.h"
19 #include "llvm/IR/LLVMContext.h"
20 #include "llvm/IR/Module.h"
21 #include "llvm/IR/ModuleSummaryIndex.h"
22 #include "llvm/IR/Verifier.h"
23 #include "llvm/Support/CommandLine.h"
24 #include "llvm/Support/FileSystem.h"
25 #include "llvm/Support/InitLLVM.h"
26 #include "llvm/Support/SourceMgr.h"
27 #include "llvm/Support/SystemUtils.h"
28 #include "llvm/Support/ToolOutputFile.h"
29 #include <memory>
30 using namespace llvm;
31 
32 cl::OptionCategory AsCat("llvm-as Options");
33 
34 static cl::opt<std::string> InputFilename(cl::Positional,
35                                           cl::desc("<input .llvm file>"),
36                                           cl::init("-"));
37 
38 static cl::opt<std::string> OutputFilename("o",
39                                            cl::desc("Override output filename"),
40                                            cl::value_desc("filename"),
41                                            cl::cat(AsCat));
42 
43 static cl::opt<bool> Force("f", cl::desc("Enable binary output on terminals"),
44                            cl::cat(AsCat));
45 
46 static cl::opt<bool> DisableOutput("disable-output", cl::desc("Disable output"),
47                                    cl::init(false), cl::cat(AsCat));
48 
49 static cl::opt<bool> EmitModuleHash("module-hash", cl::desc("Emit module hash"),
50                                     cl::init(false), cl::cat(AsCat));
51 
52 static cl::opt<bool> DumpAsm("d", cl::desc("Print assembly as parsed"),
53                              cl::Hidden, cl::cat(AsCat));
54 
55 static cl::opt<bool>
56     DisableVerify("disable-verify", cl::Hidden,
57                   cl::desc("Do not run verifier on input LLVM (dangerous!)"),
58                   cl::cat(AsCat));
59 
60 static cl::opt<bool> PreserveBitcodeUseListOrder(
61     "preserve-bc-uselistorder",
62     cl::desc("Preserve use-list order when writing LLVM bitcode."),
63     cl::init(true), cl::Hidden, cl::cat(AsCat));
64 
65 static cl::opt<std::string> ClDataLayout("data-layout",
66                                          cl::desc("data layout string to use"),
67                                          cl::value_desc("layout-string"),
68                                          cl::init(""), cl::cat(AsCat));
69 
70 static void WriteOutputFile(const Module *M, const ModuleSummaryIndex *Index) {
71   // Infer the output filename if needed.
72   if (OutputFilename.empty()) {
73     if (InputFilename == "-") {
74       OutputFilename = "-";
75     } else {
76       StringRef IFN = InputFilename;
77       OutputFilename = (IFN.endswith(".ll") ? IFN.drop_back(3) : IFN).str();
78       OutputFilename += ".bc";
79     }
80   }
81 
82   std::error_code EC;
83   std::unique_ptr<ToolOutputFile> Out(
84       new ToolOutputFile(OutputFilename, EC, sys::fs::OF_None));
85   if (EC) {
86     errs() << EC.message() << '\n';
87     exit(1);
88   }
89 
90   if (Force || !CheckBitcodeOutputToConsole(Out->os())) {
91     const ModuleSummaryIndex *IndexToWrite = nullptr;
92     // Don't attempt to write a summary index unless it contains any entries or
93     // has non-zero flags. The latter is used to assemble dummy index files for
94     // skipping modules by distributed ThinLTO backends. Otherwise we get an empty
95     // summary section.
96     if (Index && (Index->begin() != Index->end() || Index->getFlags()))
97       IndexToWrite = Index;
98     if (!IndexToWrite || (M && (!M->empty() || !M->global_empty())))
99       // If we have a non-empty Module, then we write the Module plus
100       // any non-null Index along with it as a per-module Index.
101       // If both are empty, this will give an empty module block, which is
102       // the expected behavior.
103       WriteBitcodeToFile(*M, Out->os(), PreserveBitcodeUseListOrder,
104                          IndexToWrite, EmitModuleHash);
105     else
106       // Otherwise, with an empty Module but non-empty Index, we write a
107       // combined index.
108       writeIndexToFile(*IndexToWrite, Out->os());
109   }
110 
111   // Declare success.
112   Out->keep();
113 }
114 
115 int main(int argc, char **argv) {
116   InitLLVM X(argc, argv);
117   cl::HideUnrelatedOptions(AsCat);
118   cl::ParseCommandLineOptions(argc, argv, "llvm .ll -> .bc assembler\n");
119   LLVMContext Context;
120 
121   // Parse the file now...
122   SMDiagnostic Err;
123   auto SetDataLayout = [](StringRef) -> Optional<std::string> {
124     if (ClDataLayout.empty())
125       return None;
126     return ClDataLayout;
127   };
128   ParsedModuleAndIndex ModuleAndIndex;
129   if (DisableVerify) {
130     ModuleAndIndex = parseAssemblyFileWithIndexNoUpgradeDebugInfo(
131         InputFilename, Err, Context, nullptr, SetDataLayout);
132   } else {
133     ModuleAndIndex = parseAssemblyFileWithIndex(InputFilename, Err, Context,
134                                                 nullptr, SetDataLayout);
135   }
136   std::unique_ptr<Module> M = std::move(ModuleAndIndex.Mod);
137   if (!M.get()) {
138     Err.print(argv[0], errs());
139     return 1;
140   }
141   std::unique_ptr<ModuleSummaryIndex> Index = std::move(ModuleAndIndex.Index);
142 
143   if (!DisableVerify) {
144     std::string ErrorStr;
145     raw_string_ostream OS(ErrorStr);
146     if (verifyModule(*M.get(), &OS)) {
147       errs() << argv[0]
148              << ": assembly parsed, but does not verify as correct!\n";
149       errs() << OS.str();
150       return 1;
151     }
152     // TODO: Implement and call summary index verifier.
153   }
154 
155   if (DumpAsm) {
156     errs() << "Here's the assembly:\n" << *M.get();
157     if (Index.get() && Index->begin() != Index->end())
158       Index->print(errs());
159   }
160 
161   if (!DisableOutput)
162     WriteOutputFile(M.get(), Index.get());
163 
164   return 0;
165 }
166