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/Pass.h"
15 #include "llvm/Support/CommandLine.h"
16 #include "llvm/Support/Debug.h"
17 #include "llvm/Support/raw_ostream.h"
18 using namespace llvm;
19 
20 #define DEBUG_TYPE "forceattrs"
21 
22 static cl::list<std::string>
23     ForceAttributes("force-attribute", cl::Hidden,
24                     cl::desc("Add an attribute to a function. This should be a "
25                              "pair of 'function-name:attribute-name', for "
26                              "example -force-attribute=foo:noinline. This "
27                              "option can be specified multiple times."));
28 
29 static cl::list<std::string> ForceRemoveAttributes(
30     "force-remove-attribute", cl::Hidden,
31     cl::desc("Remove an attribute from a function. This should be a "
32              "pair of 'function-name:attribute-name', for "
33              "example -force-remove-attribute=foo:noinline. This "
34              "option can be specified multiple times."));
35 
36 /// If F has any forced attributes given on the command line, add them.
37 /// If F has any forced remove attributes given on the command line, remove
38 /// them. When both force and force-remove are given to a function, the latter
39 /// takes precedence.
40 static void forceAttributes(Function &F) {
41   auto ParseFunctionAndAttr = [&](StringRef S) {
42     auto Kind = Attribute::None;
43     auto KV = StringRef(S).split(':');
44     if (KV.first != F.getName())
45       return Kind;
46     Kind = Attribute::getAttrKindFromName(KV.second);
47     if (Kind == Attribute::None || !Attribute::canUseAsFnAttr(Kind)) {
48       LLVM_DEBUG(dbgs() << "ForcedAttribute: " << KV.second
49                         << " unknown or not a function attribute!\n");
50     }
51     return Kind;
52   };
53 
54   for (const auto &S : ForceAttributes) {
55     auto Kind = ParseFunctionAndAttr(S);
56     if (Kind == Attribute::None || F.hasFnAttribute(Kind))
57       continue;
58     F.addFnAttr(Kind);
59   }
60 
61   for (const auto &S : ForceRemoveAttributes) {
62     auto Kind = ParseFunctionAndAttr(S);
63     if (Kind == Attribute::None || !F.hasFnAttribute(Kind))
64       continue;
65     F.removeFnAttr(Kind);
66   }
67 }
68 
69 static bool hasForceAttributes() {
70   return !ForceAttributes.empty() || !ForceRemoveAttributes.empty();
71 }
72 
73 PreservedAnalyses ForceFunctionAttrsPass::run(Module &M,
74                                               ModuleAnalysisManager &) {
75   if (!hasForceAttributes())
76     return PreservedAnalyses::all();
77 
78   for (Function &F : M.functions())
79     forceAttributes(F);
80 
81   // Just conservatively invalidate analyses, this isn't likely to be important.
82   return PreservedAnalyses::none();
83 }
84 
85 namespace {
86 struct ForceFunctionAttrsLegacyPass : public ModulePass {
87   static char ID; // Pass identification, replacement for typeid
88   ForceFunctionAttrsLegacyPass() : ModulePass(ID) {
89     initializeForceFunctionAttrsLegacyPassPass(
90         *PassRegistry::getPassRegistry());
91   }
92 
93   bool runOnModule(Module &M) override {
94     if (!hasForceAttributes())
95       return false;
96 
97     for (Function &F : M.functions())
98       forceAttributes(F);
99 
100     // Conservatively assume we changed something.
101     return true;
102   }
103 };
104 }
105 
106 char ForceFunctionAttrsLegacyPass::ID = 0;
107 INITIALIZE_PASS(ForceFunctionAttrsLegacyPass, "forceattrs",
108                 "Force set function attributes", false, false)
109 
110 Pass *llvm::createForceFunctionAttrsLegacyPass() {
111   return new ForceFunctionAttrsLegacyPass();
112 }
113