1 //===- DebugTranslation.cpp - MLIR to LLVM Debug conversion ---------------===//
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 #include "DebugTranslation.h"
10 #include "mlir/Dialect/LLVMIR/LLVMDialect.h"
11 #include "llvm/IR/Metadata.h"
12 #include "llvm/IR/Module.h"
13 #include "llvm/Support/FileSystem.h"
14 #include "llvm/Support/Path.h"
15 
16 using namespace mlir;
17 using namespace mlir::LLVM;
18 using namespace mlir::LLVM::detail;
19 
20 /// A utility walker that interrupts if the operation has valid debug
21 /// information.
22 static WalkResult interruptIfValidLocation(Operation *op) {
23   return op->getLoc().isa<UnknownLoc>() ? WalkResult::advance()
24                                         : WalkResult::interrupt();
25 }
26 
27 DebugTranslation::DebugTranslation(Operation *module, llvm::Module &llvmModule)
28     : builder(llvmModule), llvmCtx(llvmModule.getContext()),
29       compileUnit(nullptr) {
30 
31   // If the module has no location information, there is nothing to do.
32   if (!module->walk(interruptIfValidLocation).wasInterrupted())
33     return;
34 
35   // TODO: Several parts of this are incorrect. Different source
36   // languages may interpret different parts of the debug information
37   // differently. Frontends will also want to pipe in various information, like
38   // flags. This is fine for now as we only emit line-table information and not
39   // types or variables. This should disappear as the debug information story
40   // evolves; i.e. when we have proper attributes for LLVM debug metadata.
41   compileUnit = builder.createCompileUnit(
42       llvm::dwarf::DW_LANG_C,
43       builder.createFile(llvmModule.getModuleIdentifier(), "/"),
44       /*Producer=*/"mlir", /*isOptimized=*/true, /*Flags=*/"", /*RV=*/0);
45 
46   // Mark this module as having debug information.
47   StringRef debugVersionKey = "Debug Info Version";
48   if (!llvmModule.getModuleFlag(debugVersionKey))
49     llvmModule.addModuleFlag(llvm::Module::Warning, debugVersionKey,
50                              llvm::DEBUG_METADATA_VERSION);
51 
52   if (auto targetTripleAttr =
53           module->getAttr(LLVM::LLVMDialect::getTargetTripleAttrName())) {
54     auto targetTriple =
55         llvm::Triple(targetTripleAttr.cast<StringAttr>().getValue());
56     if (targetTriple.isKnownWindowsMSVCEnvironment()) {
57       // Dwarf debugging files will be generated by default, unless "CodeView"
58       // is set explicitly. Windows/MSVC should use CodeView instead.
59       llvmModule.addModuleFlag(llvm::Module::Warning, "CodeView", 1);
60     }
61   }
62 }
63 
64 /// Finalize the translation of debug information.
65 void DebugTranslation::finalize() { builder.finalize(); }
66 
67 /// Attempt to extract a filename for the given loc.
68 static FileLineColLoc extractFileLoc(Location loc) {
69   if (auto fileLoc = loc.dyn_cast<FileLineColLoc>())
70     return fileLoc;
71   if (auto nameLoc = loc.dyn_cast<NameLoc>())
72     return extractFileLoc(nameLoc.getChildLoc());
73   if (auto opaqueLoc = loc.dyn_cast<OpaqueLoc>())
74     return extractFileLoc(opaqueLoc.getFallbackLocation());
75   return FileLineColLoc();
76 }
77 
78 /// Translate the debug information for the given function.
79 void DebugTranslation::translate(LLVMFuncOp func, llvm::Function &llvmFunc) {
80   // If the function doesn't have location information, there is nothing to
81   // translate.
82   if (!compileUnit || !func.walk(interruptIfValidLocation).wasInterrupted())
83     return;
84 
85   // If we are to create debug info for the function, we need to ensure that all
86   // inlinable calls in it are with debug info, otherwise the LLVM verifier will
87   // complain. For now, be more restricted and treat all calls as inlinable.
88   const bool hasCallWithoutDebugInfo =
89       func.walk([](LLVM::CallOp call) {
90             return call.getLoc().isa<UnknownLoc>() ? WalkResult::interrupt()
91                                                    : WalkResult::advance();
92           })
93           .wasInterrupted();
94   if (hasCallWithoutDebugInfo)
95     return;
96 
97   FileLineColLoc fileLoc = extractFileLoc(func.getLoc());
98   auto *file = translateFile(fileLoc ? fileLoc.getFilename() : "<unknown>");
99   unsigned line = fileLoc ? fileLoc.getLine() : 0;
100 
101   // TODO: This is the bare essentials for now. We will likely end
102   // up with wrapper metadata around LLVMs metadata in the future, so this
103   // doesn't need to be smart until then.
104   llvm::DISubroutineType *type =
105       builder.createSubroutineType(builder.getOrCreateTypeArray(llvm::None));
106   llvm::DISubprogram::DISPFlags spFlags = llvm::DISubprogram::SPFlagDefinition |
107                                           llvm::DISubprogram::SPFlagOptimized;
108   llvm::DISubprogram *program =
109       builder.createFunction(compileUnit, func.getName(), func.getName(), file,
110                              line, type, line, llvm::DINode::FlagZero, spFlags);
111   llvmFunc.setSubprogram(program);
112   builder.finalizeSubprogram(program);
113 }
114 
115 //===----------------------------------------------------------------------===//
116 // Locations
117 //===----------------------------------------------------------------------===//
118 
119 /// Translate the given location to an llvm debug location.
120 const llvm::DILocation *
121 DebugTranslation::translateLoc(Location loc, llvm::DILocalScope *scope) {
122   if (!compileUnit)
123     return nullptr;
124   return translateLoc(loc, scope, /*inlinedAt=*/nullptr);
125 }
126 
127 /// Translate the given location to an llvm DebugLoc.
128 const llvm::DILocation *
129 DebugTranslation::translateLoc(Location loc, llvm::DILocalScope *scope,
130                                const llvm::DILocation *inlinedAt) {
131   // LLVM doesn't have a representation for unknown.
132   if (!scope || loc.isa<UnknownLoc>())
133     return nullptr;
134 
135   // Check for a cached instance.
136   auto existingIt = locationToLoc.find(std::make_pair(loc, scope));
137   if (existingIt != locationToLoc.end())
138     return existingIt->second;
139 
140   const llvm::DILocation *llvmLoc = nullptr;
141   if (auto callLoc = loc.dyn_cast<CallSiteLoc>()) {
142     // For callsites, the caller is fed as the inlinedAt for the callee.
143     const auto *callerLoc = translateLoc(callLoc.getCaller(), scope, inlinedAt);
144     llvmLoc = translateLoc(callLoc.getCallee(), scope, callerLoc);
145 
146   } else if (auto fileLoc = loc.dyn_cast<FileLineColLoc>()) {
147     auto *file = translateFile(fileLoc.getFilename());
148     auto *fileScope = builder.createLexicalBlockFile(scope, file);
149     llvmLoc = llvm::DILocation::get(llvmCtx, fileLoc.getLine(),
150                                     fileLoc.getColumn(), fileScope,
151                                     const_cast<llvm::DILocation *>(inlinedAt));
152 
153   } else if (auto fusedLoc = loc.dyn_cast<FusedLoc>()) {
154     ArrayRef<Location> locations = fusedLoc.getLocations();
155 
156     // For fused locations, merge each of the nodes.
157     llvmLoc = translateLoc(locations.front(), scope, inlinedAt);
158     for (Location locIt : locations.drop_front()) {
159       llvmLoc = llvm::DILocation::getMergedLocation(
160           llvmLoc, translateLoc(locIt, scope, inlinedAt));
161     }
162 
163   } else if (auto nameLoc = loc.dyn_cast<NameLoc>()) {
164     llvmLoc = translateLoc(loc.cast<NameLoc>().getChildLoc(), scope, inlinedAt);
165 
166   } else if (auto opaqueLoc = loc.dyn_cast<OpaqueLoc>()) {
167     llvmLoc = translateLoc(loc.cast<OpaqueLoc>().getFallbackLocation(), scope,
168                            inlinedAt);
169   } else {
170     llvm_unreachable("unknown location kind");
171   }
172 
173   locationToLoc.try_emplace(std::make_pair(loc, scope), llvmLoc);
174   return llvmLoc;
175 }
176 
177 /// Create an llvm debug file for the given file path.
178 llvm::DIFile *DebugTranslation::translateFile(StringRef fileName) {
179   auto *&file = fileMap[fileName];
180   if (file)
181     return file;
182 
183   // Make sure the current working directory is up-to-date.
184   if (currentWorkingDir.empty())
185     llvm::sys::fs::current_path(currentWorkingDir);
186 
187   StringRef directory = currentWorkingDir;
188   SmallString<128> dirBuf;
189   SmallString<128> fileBuf;
190   if (llvm::sys::path::is_absolute(fileName)) {
191     // Strip the common prefix (if it is more than just "/") from current
192     // directory and FileName for a more space-efficient encoding.
193     auto fileIt = llvm::sys::path::begin(fileName);
194     auto fileE = llvm::sys::path::end(fileName);
195     auto curDirIt = llvm::sys::path::begin(directory);
196     auto curDirE = llvm::sys::path::end(directory);
197     for (; curDirIt != curDirE && *curDirIt == *fileIt; ++curDirIt, ++fileIt)
198       llvm::sys::path::append(dirBuf, *curDirIt);
199     if (std::distance(llvm::sys::path::begin(directory), curDirIt) == 1) {
200       // Don't strip the common prefix if it is only the root "/"  since that
201       // would make LLVM diagnostic locations confusing.
202       directory = StringRef();
203     } else {
204       for (; fileIt != fileE; ++fileIt)
205         llvm::sys::path::append(fileBuf, *fileIt);
206       directory = dirBuf;
207       fileName = fileBuf;
208     }
209   }
210   return (file = builder.createFile(fileName, directory));
211 }
212