1 //===-- NVPTXTargetTransformInfo.h - NVPTX specific TTI ---------*- C++ -*-===//
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 /// \file
9 /// This file a TargetTransformInfo::Concept conforming object specific to the
10 /// NVPTX target machine. It uses the target's detailed information to
11 /// provide more precise answers to certain TTI queries, while letting the
12 /// target independent and default TTI implementations handle the rest.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_LIB_TARGET_NVPTX_NVPTXTARGETTRANSFORMINFO_H
17 #define LLVM_LIB_TARGET_NVPTX_NVPTXTARGETTRANSFORMINFO_H
18 
19 #include "NVPTXTargetMachine.h"
20 #include "MCTargetDesc/NVPTXBaseInfo.h"
21 #include "llvm/Analysis/TargetTransformInfo.h"
22 #include "llvm/CodeGen/BasicTTIImpl.h"
23 #include "llvm/CodeGen/TargetLowering.h"
24 
25 namespace llvm {
26 
27 class NVPTXTTIImpl : public BasicTTIImplBase<NVPTXTTIImpl> {
28   typedef BasicTTIImplBase<NVPTXTTIImpl> BaseT;
29   typedef TargetTransformInfo TTI;
30   friend BaseT;
31 
32   const NVPTXSubtarget *ST;
33   const NVPTXTargetLowering *TLI;
34 
35   const NVPTXSubtarget *getST() const { return ST; };
36   const NVPTXTargetLowering *getTLI() const { return TLI; };
37 
38 public:
39   explicit NVPTXTTIImpl(const NVPTXTargetMachine *TM, const Function &F)
40       : BaseT(TM, F.getParent()->getDataLayout()), ST(TM->getSubtargetImpl()),
41         TLI(ST->getTargetLowering()) {}
42 
43   bool hasBranchDivergence() { return true; }
44 
45   bool isSourceOfDivergence(const Value *V);
46 
47   unsigned getFlatAddressSpace() const {
48     return AddressSpace::ADDRESS_SPACE_GENERIC;
49   }
50 
51   // Loads and stores can be vectorized if the alignment is at least as big as
52   // the load/store we want to vectorize.
53   bool isLegalToVectorizeLoadChain(unsigned ChainSizeInBytes,
54                                    unsigned Alignment,
55                                    unsigned AddrSpace) const {
56     return Alignment >= ChainSizeInBytes;
57   }
58   bool isLegalToVectorizeStoreChain(unsigned ChainSizeInBytes,
59                                     unsigned Alignment,
60                                     unsigned AddrSpace) const {
61     return isLegalToVectorizeLoadChain(ChainSizeInBytes, Alignment, AddrSpace);
62   }
63 
64   // NVPTX has infinite registers of all kinds, but the actual machine doesn't.
65   // We conservatively return 1 here which is just enough to enable the
66   // vectorizers but disables heuristics based on the number of registers.
67   // FIXME: Return a more reasonable number, while keeping an eye on
68   // LoopVectorizer's unrolling heuristics.
69   unsigned getNumberOfRegisters(bool Vector) const { return 1; }
70 
71   // Only <2 x half> should be vectorized, so always return 32 for the vector
72   // register size.
73   unsigned getRegisterBitWidth(bool Vector) const { return 32; }
74   unsigned getMinVectorRegisterBitWidth() const { return 32; }
75 
76   // We don't want to prevent inlining because of target-cpu and -features
77   // attributes that were added to newer versions of LLVM/Clang: There are
78   // no incompatible functions in PTX, ptxas will throw errors in such cases.
79   bool areInlineCompatible(const Function *Caller,
80                            const Function *Callee) const {
81     return true;
82   }
83 
84   // Increase the inlining cost threshold by a factor of 5, reflecting that
85   // calls are particularly expensive in NVPTX.
86   unsigned getInliningThresholdMultiplier() { return 5; }
87 
88   int getArithmeticInstrCost(
89       unsigned Opcode, Type *Ty,
90       TTI::OperandValueKind Opd1Info = TTI::OK_AnyValue,
91       TTI::OperandValueKind Opd2Info = TTI::OK_AnyValue,
92       TTI::OperandValueProperties Opd1PropInfo = TTI::OP_None,
93       TTI::OperandValueProperties Opd2PropInfo = TTI::OP_None,
94       ArrayRef<const Value *> Args = ArrayRef<const Value *>());
95 
96   void getUnrollingPreferences(Loop *L, ScalarEvolution &SE,
97                                TTI::UnrollingPreferences &UP);
98   bool hasVolatileVariant(Instruction *I, unsigned AddrSpace) {
99     // Volatile loads/stores are only supported for shared and global address
100     // spaces, or for generic AS that maps to them.
101     if (!(AddrSpace == llvm::ADDRESS_SPACE_GENERIC ||
102           AddrSpace == llvm::ADDRESS_SPACE_GLOBAL ||
103           AddrSpace == llvm::ADDRESS_SPACE_SHARED))
104       return false;
105 
106     switch(I->getOpcode()){
107     default:
108       return false;
109     case Instruction::Load:
110     case Instruction::Store:
111       return true;
112     }
113   }
114 };
115 
116 } // end namespace llvm
117 
118 #endif
119