1 //===-- PPCGenScalarMASSEntries.cpp ---------------------------------------===//
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 transformation converts standard math functions into their
10 // corresponding MASS (scalar) entries for PowerPC targets.
11 // Following are examples of such conversion:
12 // tanh ---> __xl_tanh_finite
13 // Such lowering is legal under the fast-math option.
14 //
15 //===----------------------------------------------------------------------===//
16
17 #include "PPC.h"
18 #include "PPCSubtarget.h"
19 #include "PPCTargetMachine.h"
20 #include "llvm/Analysis/TargetTransformInfo.h"
21 #include "llvm/CodeGen/TargetPassConfig.h"
22 #include "llvm/IR/Instructions.h"
23 #include "llvm/IR/Module.h"
24
25 #define DEBUG_TYPE "ppc-gen-scalar-mass"
26
27 using namespace llvm;
28
29 namespace {
30
31 class PPCGenScalarMASSEntries : public ModulePass {
32 public:
33 static char ID;
34
PPCGenScalarMASSEntries()35 PPCGenScalarMASSEntries() : ModulePass(ID) {
36 ScalarMASSFuncs = {
37 #define TLI_DEFINE_SCALAR_MASS_FUNCS
38 #include "llvm/Analysis/ScalarFuncs.def"
39 };
40 }
41
42 bool runOnModule(Module &M) override;
43
getPassName() const44 StringRef getPassName() const override {
45 return "PPC Generate Scalar MASS Entries";
46 }
47
getAnalysisUsage(AnalysisUsage & AU) const48 void getAnalysisUsage(AnalysisUsage &AU) const override {
49 AU.addRequired<TargetTransformInfoWrapperPass>();
50 }
51
52 private:
53 std::map<StringRef, StringRef> ScalarMASSFuncs;
54 bool isCandidateSafeToLower(const CallInst &CI) const;
55 bool isFiniteCallSafe(const CallInst &CI) const;
56 bool createScalarMASSCall(StringRef MASSEntry, CallInst &CI,
57 Function &Func) const;
58 };
59
60 } // namespace
61
62 // Returns true if 'afn' flag exists on the call instruction with the math
63 // function
isCandidateSafeToLower(const CallInst & CI) const64 bool PPCGenScalarMASSEntries::isCandidateSafeToLower(const CallInst &CI) const {
65 // skip functions with no scalar or vector FP type (like cosisin)
66 if (!isa<FPMathOperator>(CI))
67 return false;
68
69 return CI.hasApproxFunc();
70 }
71
72 // Returns true if 'nnan', 'ninf' and 'nsz' flags exist on the call instruction
73 // with the math function
isFiniteCallSafe(const CallInst & CI) const74 bool PPCGenScalarMASSEntries::isFiniteCallSafe(const CallInst &CI) const {
75 // skip functions with no scalar or vector FP type (like cosisin)
76 if (!isa<FPMathOperator>(CI))
77 return false;
78
79 // FIXME: no-errno and trapping-math need to be set for MASS converstion
80 // but they don't have IR representation.
81 return CI.hasNoNaNs() && CI.hasNoInfs() && CI.hasNoSignedZeros();
82 }
83
84 /// Lowers scalar math functions to scalar MASS functions.
85 /// e.g.: tanh --> __xl_tanh_finite or __xl_tanh
86 /// Both function prototype and its callsite is updated during lowering.
createScalarMASSCall(StringRef MASSEntry,CallInst & CI,Function & Func) const87 bool PPCGenScalarMASSEntries::createScalarMASSCall(StringRef MASSEntry,
88 CallInst &CI,
89 Function &Func) const {
90 if (CI.use_empty())
91 return false;
92
93 Module *M = Func.getParent();
94 assert(M && "Expecting a valid Module");
95
96 std::string MASSEntryStr = MASSEntry.str();
97 if (isFiniteCallSafe(CI))
98 MASSEntryStr += "_finite";
99
100 FunctionCallee FCache = M->getOrInsertFunction(
101 MASSEntryStr, Func.getFunctionType(), Func.getAttributes());
102
103 CI.setCalledFunction(FCache);
104
105 return true;
106 }
107
runOnModule(Module & M)108 bool PPCGenScalarMASSEntries::runOnModule(Module &M) {
109 bool Changed = false;
110
111 auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
112 if (!TPC || skipModule(M))
113 return false;
114
115 for (Function &Func : M) {
116 if (!Func.isDeclaration())
117 continue;
118
119 auto Iter = ScalarMASSFuncs.find(Func.getName());
120 if (Iter == ScalarMASSFuncs.end())
121 continue;
122
123 // The call to createScalarMASSCall() invalidates the iterator over users
124 // upon replacing the users. Precomputing the current list of users allows
125 // us to replace all the call sites.
126 SmallVector<User *, 4> TheUsers;
127 for (auto *User : Func.users())
128 TheUsers.push_back(User);
129
130 for (auto *User : TheUsers)
131 if (auto *CI = dyn_cast_or_null<CallInst>(User)) {
132 if (isCandidateSafeToLower(*CI))
133 Changed |= createScalarMASSCall(Iter->second, *CI, Func);
134 }
135 }
136
137 return Changed;
138 }
139
140 char PPCGenScalarMASSEntries::ID = 0;
141
142 char &llvm::PPCGenScalarMASSEntriesID = PPCGenScalarMASSEntries::ID;
143
144 INITIALIZE_PASS(PPCGenScalarMASSEntries, DEBUG_TYPE,
145 "Generate Scalar MASS entries", false, false)
146
createPPCGenScalarMASSEntriesPass()147 ModulePass *llvm::createPPCGenScalarMASSEntriesPass() {
148 return new PPCGenScalarMASSEntries();
149 }
150