1 //===-- PPCLowerMASSVEntries.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 file implements lowering of MASSV (SIMD) entries for specific PowerPC
10 // subtargets.
11 // Following is an example of a conversion specific to Power9 subtarget:
12 // __sind2_massv ---> __sind2_P9
13 //
14 //===----------------------------------------------------------------------===//
15
16 #include "PPC.h"
17 #include "PPCSubtarget.h"
18 #include "PPCTargetMachine.h"
19 #include "llvm/ADT/STLExtras.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-lower-massv-entries"
26
27 using namespace llvm;
28
29 namespace {
30
31 static StringRef MASSVFuncs[] = {
32 #define TLI_DEFINE_MASSV_VECFUNCS_NAMES
33 #include "llvm/Analysis/VecFuncs.def"
34 };
35
36 class PPCLowerMASSVEntries : public ModulePass {
37 public:
38 static char ID;
39
PPCLowerMASSVEntries()40 PPCLowerMASSVEntries() : ModulePass(ID) {}
41
42 bool runOnModule(Module &M) override;
43
getPassName() const44 StringRef getPassName() const override { return "PPC Lower MASS Entries"; }
45
getAnalysisUsage(AnalysisUsage & AU) const46 void getAnalysisUsage(AnalysisUsage &AU) const override {
47 AU.addRequired<TargetTransformInfoWrapperPass>();
48 }
49
50 private:
51 static bool isMASSVFunc(StringRef Name);
52 static StringRef getCPUSuffix(const PPCSubtarget *Subtarget);
53 static std::string createMASSVFuncName(Function &Func,
54 const PPCSubtarget *Subtarget);
55 bool handlePowSpecialCases(CallInst *CI, Function &Func, Module &M);
56 bool lowerMASSVCall(CallInst *CI, Function &Func, Module &M,
57 const PPCSubtarget *Subtarget);
58 };
59
60 } // namespace
61
62 /// Checks if the specified function name represents an entry in the MASSV
63 /// library.
isMASSVFunc(StringRef Name)64 bool PPCLowerMASSVEntries::isMASSVFunc(StringRef Name) {
65 return llvm::is_contained(MASSVFuncs, Name);
66 }
67
68 // FIXME:
69 /// Returns a string corresponding to the specified PowerPC subtarget. e.g.:
70 /// "_P8" for Power8, "_P9" for Power9. The string is used as a suffix while
71 /// generating subtarget-specific MASSV library functions. Current support
72 /// includes minimum subtarget Power8 for Linux and Power7 for AIX.
getCPUSuffix(const PPCSubtarget * Subtarget)73 StringRef PPCLowerMASSVEntries::getCPUSuffix(const PPCSubtarget *Subtarget) {
74 // Assume generic when Subtarget is unavailable.
75 if (!Subtarget)
76 return "";
77 // TODO: add _P10 enties to Linux MASS lib and remove the check for AIX
78 if (Subtarget->isAIXABI() && Subtarget->hasP10Vector())
79 return "_P10";
80 if (Subtarget->hasP9Vector())
81 return "_P9";
82 if (Subtarget->hasP8Vector())
83 return "_P8";
84 if (Subtarget->isAIXABI())
85 return "_P7";
86
87 report_fatal_error(
88 "Mininum subtarget for -vector-library=MASSV option is Power8 on Linux "
89 "and Power7 on AIX when vectorization is not disabled.");
90 }
91
92 /// Creates PowerPC subtarget-specific name corresponding to the specified
93 /// generic MASSV function, and the PowerPC subtarget.
94 std::string
createMASSVFuncName(Function & Func,const PPCSubtarget * Subtarget)95 PPCLowerMASSVEntries::createMASSVFuncName(Function &Func,
96 const PPCSubtarget *Subtarget) {
97 StringRef Suffix = getCPUSuffix(Subtarget);
98 auto GenericName = Func.getName().str();
99 std::string MASSVEntryName = GenericName + Suffix.str();
100 return MASSVEntryName;
101 }
102
103 /// If there are proper fast-math flags, this function creates llvm.pow
104 /// intrinsics when the exponent is 0.25 or 0.75.
handlePowSpecialCases(CallInst * CI,Function & Func,Module & M)105 bool PPCLowerMASSVEntries::handlePowSpecialCases(CallInst *CI, Function &Func,
106 Module &M) {
107 if (Func.getName() != "__powf4" && Func.getName() != "__powd2")
108 return false;
109
110 if (Constant *Exp = dyn_cast<Constant>(CI->getArgOperand(1)))
111 if (ConstantFP *CFP = dyn_cast_or_null<ConstantFP>(Exp->getSplatValue())) {
112 // If the argument is 0.75 or 0.25 it is cheaper to turn it into pow
113 // intrinsic so that it could be optimzed as sequence of sqrt's.
114 if (!CI->hasNoInfs() || !CI->hasApproxFunc())
115 return false;
116
117 if (!CFP->isExactlyValue(0.75) && !CFP->isExactlyValue(0.25))
118 return false;
119
120 if (CFP->isExactlyValue(0.25) && !CI->hasNoSignedZeros())
121 return false;
122
123 CI->setCalledFunction(
124 Intrinsic::getDeclaration(&M, Intrinsic::pow, CI->getType()));
125 return true;
126 }
127
128 return false;
129 }
130
131 /// Lowers generic MASSV entries to PowerPC subtarget-specific MASSV entries.
132 /// e.g.: __sind2_massv --> __sind2_P9 for a Power9 subtarget.
133 /// Both function prototypes and their callsites are updated during lowering.
lowerMASSVCall(CallInst * CI,Function & Func,Module & M,const PPCSubtarget * Subtarget)134 bool PPCLowerMASSVEntries::lowerMASSVCall(CallInst *CI, Function &Func,
135 Module &M,
136 const PPCSubtarget *Subtarget) {
137 if (CI->use_empty())
138 return false;
139
140 // Handling pow(x, 0.25), pow(x, 0.75), powf(x, 0.25), powf(x, 0.75)
141 if (handlePowSpecialCases(CI, Func, M))
142 return true;
143
144 std::string MASSVEntryName = createMASSVFuncName(Func, Subtarget);
145 FunctionCallee FCache = M.getOrInsertFunction(
146 MASSVEntryName, Func.getFunctionType(), Func.getAttributes());
147
148 CI->setCalledFunction(FCache);
149
150 return true;
151 }
152
runOnModule(Module & M)153 bool PPCLowerMASSVEntries::runOnModule(Module &M) {
154 bool Changed = false;
155
156 auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
157 if (!TPC)
158 return Changed;
159
160 auto &TM = TPC->getTM<PPCTargetMachine>();
161 const PPCSubtarget *Subtarget;
162
163 for (Function &Func : M) {
164 if (!Func.isDeclaration())
165 continue;
166
167 if (!isMASSVFunc(Func.getName()))
168 continue;
169
170 // Call to lowerMASSVCall() invalidates the iterator over users upon
171 // replacing the users. Precomputing the current list of users allows us to
172 // replace all the call sites.
173 SmallVector<User *, 4> MASSVUsers(Func.users());
174
175 for (auto *User : MASSVUsers) {
176 auto *CI = dyn_cast<CallInst>(User);
177 if (!CI)
178 continue;
179
180 Subtarget = &TM.getSubtarget<PPCSubtarget>(*CI->getParent()->getParent());
181 Changed |= lowerMASSVCall(CI, Func, M, Subtarget);
182 }
183 }
184
185 return Changed;
186 }
187
188 char PPCLowerMASSVEntries::ID = 0;
189
190 char &llvm::PPCLowerMASSVEntriesID = PPCLowerMASSVEntries::ID;
191
192 INITIALIZE_PASS(PPCLowerMASSVEntries, DEBUG_TYPE, "Lower MASSV entries", false,
193 false)
194
createPPCLowerMASSVEntriesPass()195 ModulePass *llvm::createPPCLowerMASSVEntriesPass() {
196 return new PPCLowerMASSVEntries();
197 }
198