llvm/lib/Transforms/IPO/ForceFunctionAttrs.cpp

   1 //===- ForceFunctionAttrs.cpp - Force function attrs for debugging --------===//
   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 "llvm/Transforms/IPO/ForceFunctionAttrs.h"
  10 #include "llvm/IR/Function.h"
  11 #include "llvm/IR/Module.h"
  12 #include "llvm/Support/CommandLine.h"
  13 #include "llvm/Support/Debug.h"
  14 #include "llvm/Support/LineIterator.h"
  15 #include "llvm/Support/MemoryBuffer.h"
  16 #include "llvm/Support/raw_ostream.h"
  17 using namespace llvm;
  18
  19 #define DEBUG_TYPE "forceattrs"
  20
  21 static cl::list<std::string> ForceAttributes(
  22     "force-attribute", cl::Hidden,
  23     cl::desc(
  24         "Add an attribute to a function. This can be a "
  25         "pair of 'function-name:attribute-name', to apply an attribute to a "
  26         "specific function. For "
  27         "example -force-attribute=foo:noinline. Specifying only an attribute "
  28         "will apply the attribute to every function in the module. This "
  29         "option can be specified multiple times."));
  30
  31 static cl::list<std::string> ForceRemoveAttributes(
  32     "force-remove-attribute", cl::Hidden,
  33     cl::desc("Remove an attribute from a function. This can be a "
  34              "pair of 'function-name:attribute-name' to remove an attribute "
  35              "from a specific function. For "
  36              "example -force-remove-attribute=foo:noinline. Specifying only an "
  37              "attribute will remove the attribute from all functions in the "
  38              "module. This "
  39              "option can be specified multiple times."));
  40
  41 static cl::opt<std::string> CSVFilePath(
  42     "forceattrs-csv-path", cl::Hidden,
  43     cl::desc(
  44         "Path to CSV file containing lines of function names and attributes to "
  45         "add to them in the form of `f1,attr1` or `f2,attr2=str`."));
  46
  47 /// If F has any forced attributes given on the command line, add them.
  48 /// If F has any forced remove attributes given on the command line, remove
  49 /// them. When both force and force-remove are given to a function, the latter
  50 /// takes precedence.
  51 static void forceAttributes(Function &F) {
  52   auto ParseFunctionAndAttr = [&](StringRef S) {
  53     StringRef AttributeText;
  54     if (S.contains(':')) {
  55       auto KV = StringRef(S).split(':');
  56       if (KV.first != F.getName())
  57         return Attribute::None;
  58       AttributeText = KV.second;
  59     } else {
  60       AttributeText = S;
  61     }
  62     auto Kind = Attribute::getAttrKindFromName(AttributeText);
  63     if (Kind == Attribute::None || !Attribute::canUseAsFnAttr(Kind)) {
  64       LLVM_DEBUG(dbgs() << "ForcedAttribute: " << AttributeText
  65                         << " unknown or not a function attribute!\n");
  66     }
  67     return Kind;
  68   };
  69
  70   for (const auto &S : ForceAttributes) {
  71     auto Kind = ParseFunctionAndAttr(S);
  72     if (Kind == Attribute::None || F.hasFnAttribute(Kind))
  73       continue;
  74     F.addFnAttr(Kind);
  75   }
  76
  77   for (const auto &S : ForceRemoveAttributes) {
  78     auto Kind = ParseFunctionAndAttr(S);
  79     if (Kind == Attribute::None || !F.hasFnAttribute(Kind))
  80       continue;
  81     F.removeFnAttr(Kind);
  82   }
  83 }
  84
  85 static bool hasForceAttributes() {
  86   return !ForceAttributes.empty() || !ForceRemoveAttributes.empty();
  87 }
  88
  89 PreservedAnalyses ForceFunctionAttrsPass::run(Module &M,
  90                                               ModuleAnalysisManager &) {
  91   bool Changed = false;
  92   if (!CSVFilePath.empty()) {
  93     auto BufferOrError = MemoryBuffer::getFileOrSTDIN(CSVFilePath);
  94     if (!BufferOrError)
  95       report_fatal_error("Cannot open CSV file.");
  96     StringRef Buffer = BufferOrError.get()->getBuffer();
  97     auto MemoryBuffer = MemoryBuffer::getMemBuffer(Buffer);
  98     line_iterator It(*MemoryBuffer);
  99     for (; !It.is_at_end(); ++It) {
 100       auto SplitPair = It->split(',');
 101       if (SplitPair.second.empty())
 102         continue;
 103       Function *Func = M.getFunction(SplitPair.first);
 104       if (Func) {
 105         if (Func->isDeclaration())
 106           continue;
 107         auto SecondSplitPair = SplitPair.second.split('=');
 108         if (!SecondSplitPair.second.empty()) {
 109           Func->addFnAttr(SecondSplitPair.first, SecondSplitPair.second);
 110           Changed = true;
 111         } else {
 112           auto AttrKind = Attribute::getAttrKindFromName(SplitPair.second);
 113           if (AttrKind != Attribute::None &&
 114               Attribute::canUseAsFnAttr(AttrKind)) {
 115             // TODO: There could be string attributes without a value, we should
 116             // support those, too.
 117             Func->addFnAttr(AttrKind);
 118             Changed = true;
 119           } else
 120             errs() << "Cannot add " << SplitPair.second
 121                    << " as an attribute name.\n";
 122         }
 123       } else {
 124         errs() << "Function in CSV file at line " << It.line_number()
 125                << " does not exist.\n";
 126         // TODO: `report_fatal_error at end of pass for missing functions.
 127         continue;
 128       }
 129     }
 130   }
 131   if (hasForceAttributes()) {
 132     for (Function &F : M.functions())
 133       forceAttributes(F);
 134     Changed = true;
 135   }
 136   // Just conservatively invalidate analyses if we've made any changes, this
 137   // isn't likely to be important.
 138   return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
 139 }