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/ManagedStatic.h"
27 #include "llvm/Support/SourceMgr.h"
28 #include "llvm/Support/SystemUtils.h"
29 #include "llvm/Support/ToolOutputFile.h"
30 #include <memory>
31 using namespace llvm;
32 
33 cl::OptionCategory AsCat("llvm-as Options");
34 
35 static cl::opt<std::string> InputFilename(cl::Positional,
36                                           cl::desc("<input .llvm file>"),
37                                           cl::init("-"));
38 
39 static cl::opt<std::string> OutputFilename("o",
40                                            cl::desc("Override output filename"),
41                                            cl::value_desc("filename"),
42                                            cl::cat(AsCat));
43 
44 static cl::opt<bool> Force("f", cl::desc("Enable binary output on terminals"),
45                            cl::cat(AsCat));
46 
47 static cl::opt<bool> DisableOutput("disable-output", cl::desc("Disable output"),
48                                    cl::init(false), cl::cat(AsCat));
49 
50 static cl::opt<bool> EmitModuleHash("module-hash", cl::desc("Emit module hash"),
51                                     cl::init(false), cl::cat(AsCat));
52 
53 static cl::opt<bool> DumpAsm("d", cl::desc("Print assembly as parsed"),
54                              cl::Hidden, cl::cat(AsCat));
55 
56 static cl::opt<bool>
57     DisableVerify("disable-verify", cl::Hidden,
58                   cl::desc("Do not run verifier on input LLVM (dangerous!)"),
59                   cl::cat(AsCat));
60 
61 static cl::opt<bool> PreserveBitcodeUseListOrder(
62     "preserve-bc-uselistorder",
63     cl::desc("Preserve use-list order when writing LLVM bitcode."),
64     cl::init(true), cl::Hidden, cl::cat(AsCat));
65 
66 static cl::opt<std::string> ClDataLayout("data-layout",
67                                          cl::desc("data layout string to use"),
68                                          cl::value_desc("layout-string"),
69                                          cl::init(""), cl::cat(AsCat));
70 
71 static void WriteOutputFile(const Module *M, const ModuleSummaryIndex *Index) {
72   // Infer the output filename if needed.
73   if (OutputFilename.empty()) {
74     if (InputFilename == "-") {
75       OutputFilename = "-";
76     } else {
77       StringRef IFN = InputFilename;
78       OutputFilename = (IFN.endswith(".ll") ? IFN.drop_back(3) : IFN).str();
79       OutputFilename += ".bc";
80     }
81   }
82 
83   std::error_code EC;
84   std::unique_ptr<ToolOutputFile> Out(
85       new ToolOutputFile(OutputFilename, EC, sys::fs::OF_None));
86   if (EC) {
87     errs() << EC.message() << '\n';
88     exit(1);
89   }
90 
91   if (Force || !CheckBitcodeOutputToConsole(Out->os())) {
92     const ModuleSummaryIndex *IndexToWrite = nullptr;
93     // Don't attempt to write a summary index unless it contains any entries or
94     // has non-zero flags. The latter is used to assemble dummy index files for
95     // skipping modules by distributed ThinLTO backends. Otherwise we get an empty
96     // summary section.
97     if (Index && (Index->begin() != Index->end() || Index->getFlags()))
98       IndexToWrite = Index;
99     if (!IndexToWrite || (M && (!M->empty() || !M->global_empty())))
100       // If we have a non-empty Module, then we write the Module plus
101       // any non-null Index along with it as a per-module Index.
102       // If both are empty, this will give an empty module block, which is
103       // the expected behavior.
104       WriteBitcodeToFile(*M, Out->os(), PreserveBitcodeUseListOrder,
105                          IndexToWrite, EmitModuleHash);
106     else
107       // Otherwise, with an empty Module but non-empty Index, we write a
108       // combined index.
109       WriteIndexToFile(*IndexToWrite, Out->os());
110   }
111 
112   // Declare success.
113   Out->keep();
114 }
115 
116 int main(int argc, char **argv) {
117   InitLLVM X(argc, argv);
118   cl::HideUnrelatedOptions(AsCat);
119   cl::ParseCommandLineOptions(argc, argv, "llvm .ll -> .bc assembler\n");
120   LLVMContext Context;
121 
122   // Parse the file now...
123   SMDiagnostic Err;
124   auto SetDataLayout = [](StringRef) -> Optional<std::string> {
125     if (ClDataLayout.empty())
126       return None;
127     return ClDataLayout;
128   };
129   ParsedModuleAndIndex ModuleAndIndex;
130   if (DisableVerify) {
131     ModuleAndIndex = parseAssemblyFileWithIndexNoUpgradeDebugInfo(
132         InputFilename, Err, Context, nullptr, SetDataLayout);
133   } else {
134     ModuleAndIndex = parseAssemblyFileWithIndex(InputFilename, Err, Context,
135                                                 nullptr, SetDataLayout);
136   }
137   std::unique_ptr<Module> M = std::move(ModuleAndIndex.Mod);
138   if (!M.get()) {
139     Err.print(argv[0], errs());
140     return 1;
141   }
142   std::unique_ptr<ModuleSummaryIndex> Index = std::move(ModuleAndIndex.Index);
143 
144   if (!DisableVerify) {
145     std::string ErrorStr;
146     raw_string_ostream OS(ErrorStr);
147     if (verifyModule(*M.get(), &OS)) {
148       errs() << argv[0]
149              << ": assembly parsed, but does not verify as correct!\n";
150       errs() << OS.str();
151       return 1;
152     }
153     // TODO: Implement and call summary index verifier.
154   }
155 
156   if (DumpAsm) {
157     errs() << "Here's the assembly:\n" << *M.get();
158     if (Index.get() && Index->begin() != Index->end())
159       Index->print(errs());
160   }
161 
162   if (!DisableOutput)
163     WriteOutputFile(M.get(), Index.get());
164 
165   return 0;
166 }
167