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/LLVMContext.h"
12 #include "llvm/IR/Module.h"
13 #include "llvm/InitializePasses.h"
14 #include "llvm/Support/CommandLine.h"
15 #include "llvm/Support/Debug.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>
22     ForceAttributes("force-attribute", cl::Hidden,
23                     cl::desc("Add an attribute to a function. This should be a "
24                              "pair of 'function-name:attribute-name', for "
25                              "example -force-attribute=foo:noinline. This "
26                              "option can be specified multiple times."));
27 
28 static cl::list<std::string> ForceRemoveAttributes(
29     "force-remove-attribute", cl::Hidden,
30     cl::desc("Remove an attribute from a function. This should be a "
31              "pair of 'function-name:attribute-name', for "
32              "example -force-remove-attribute=foo:noinline. This "
33              "option can be specified multiple times."));
34 
35 /// If F has any forced attributes given on the command line, add them.
36 /// If F has any forced remove attributes given on the command line, remove
37 /// them. When both force and force-remove are given to a function, the latter
38 /// takes precedence.
39 static void forceAttributes(Function &F) {
40   auto ParseFunctionAndAttr = [&](StringRef S) {
41     auto Kind = Attribute::None;
42     auto KV = StringRef(S).split(':');
43     if (KV.first != F.getName())
44       return Kind;
45     Kind = Attribute::getAttrKindFromName(KV.second);
46     if (Kind == Attribute::None || !Attribute::canUseAsFnAttr(Kind)) {
47       LLVM_DEBUG(dbgs() << "ForcedAttribute: " << KV.second
48                         << " unknown or not a function attribute!\n");
49     }
50     return Kind;
51   };
52 
53   for (const auto &S : ForceAttributes) {
54     auto Kind = ParseFunctionAndAttr(S);
55     if (Kind == Attribute::None || F.hasFnAttribute(Kind))
56       continue;
57     F.addFnAttr(Kind);
58   }
59 
60   for (const auto &S : ForceRemoveAttributes) {
61     auto Kind = ParseFunctionAndAttr(S);
62     if (Kind == Attribute::None || !F.hasFnAttribute(Kind))
63       continue;
64     F.removeFnAttr(Kind);
65   }
66 }
67 
68 static bool hasForceAttributes() {
69   return !ForceAttributes.empty() || !ForceRemoveAttributes.empty();
70 }
71 
72 PreservedAnalyses ForceFunctionAttrsPass::run(Module &M,
73                                               ModuleAnalysisManager &) {
74   if (!hasForceAttributes())
75     return PreservedAnalyses::all();
76 
77   for (Function &F : M.functions())
78     forceAttributes(F);
79 
80   // Just conservatively invalidate analyses, this isn't likely to be important.
81   return PreservedAnalyses::none();
82 }
83 
84 namespace {
85 struct ForceFunctionAttrsLegacyPass : public ModulePass {
86   static char ID; // Pass identification, replacement for typeid
87   ForceFunctionAttrsLegacyPass() : ModulePass(ID) {
88     initializeForceFunctionAttrsLegacyPassPass(
89         *PassRegistry::getPassRegistry());
90   }
91 
92   bool runOnModule(Module &M) override {
93     if (!hasForceAttributes())
94       return false;
95 
96     for (Function &F : M.functions())
97       forceAttributes(F);
98 
99     // Conservatively assume we changed something.
100     return true;
101   }
102 };
103 }
104 
105 char ForceFunctionAttrsLegacyPass::ID = 0;
106 INITIALIZE_PASS(ForceFunctionAttrsLegacyPass, "forceattrs",
107                 "Force set function attributes", false, false)
108 
109 Pass *llvm::createForceFunctionAttrsLegacyPass() {
110   return new ForceFunctionAttrsLegacyPass();
111 }
112