1 //===--------------------- Support.h ----------------------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 /// \file
10 ///
11 /// Helper functions used by various pipeline components.
12 ///
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_MCA_SUPPORT_H
16 #define LLVM_MCA_SUPPORT_H
17 
18 #include "llvm/ADT/ArrayRef.h"
19 #include "llvm/ADT/SmallVector.h"
20 #include "llvm/MC/MCSchedule.h"
21 #include "llvm/Support/Error.h"
22 
23 namespace llvm {
24 namespace mca {
25 
26 template <typename T>
27 class InstructionError : public ErrorInfo<InstructionError<T>> {
28 public:
29   static char ID;
30   std::string Message;
31   const T &Inst;
32 
33   InstructionError(std::string M, const T &MCI)
34       : Message(std::move(M)), Inst(MCI) {}
35 
36   void log(raw_ostream &OS) const override { OS << Message; }
37 
38   std::error_code convertToErrorCode() const override {
39     return inconvertibleErrorCode();
40   }
41 };
42 
43 template <typename T> char InstructionError<T>::ID;
44 
45 /// This class represents the number of cycles per resource (fractions of
46 /// cycles).  That quantity is managed here as a ratio, and accessed via the
47 /// double cast-operator below.  The two quantities, number of cycles and
48 /// number of resources, are kept separate.  This is used by the
49 /// ResourcePressureView to calculate the average resource cycles
50 /// per instruction/iteration.
51 class ResourceCycles {
52   unsigned Numerator, Denominator;
53 
54 public:
55   ResourceCycles() : Numerator(0), Denominator(1) {}
56   ResourceCycles(unsigned Cycles, unsigned ResourceUnits = 1)
57       : Numerator(Cycles), Denominator(ResourceUnits) {}
58 
59   operator double() const {
60     assert(Denominator && "Invalid denominator (must be non-zero).");
61     return (Denominator == 1) ? Numerator : (double)Numerator / Denominator;
62   }
63 
64   // Add the components of RHS to this instance.  Instead of calculating
65   // the final value here, we keep track of the numerator and denominator
66   // separately, to reduce floating point error.
67   ResourceCycles &operator+=(const ResourceCycles &RHS) {
68     if (Denominator == RHS.Denominator)
69       Numerator += RHS.Numerator;
70     else {
71       // Create a common denominator for LHS and RHS by calculating the least
72       // common multiple from the GCD.
73       unsigned GCD = GreatestCommonDivisor64(Denominator, RHS.Denominator);
74       unsigned LCM = (Denominator * RHS.Denominator) / GCD;
75       unsigned LHSNumerator = Numerator * (LCM / Denominator);
76       unsigned RHSNumerator = RHS.Numerator * (LCM / RHS.Denominator);
77       Numerator = LHSNumerator + RHSNumerator;
78       Denominator = LCM;
79     }
80     return *this;
81   }
82 };
83 
84 /// Populates vector Masks with processor resource masks.
85 ///
86 /// The number of bits set in a mask depends on the processor resource type.
87 /// Each processor resource mask has at least one bit set. For groups, the
88 /// number of bits set in the mask is equal to the cardinality of the group plus
89 /// one. Excluding the most significant bit, the remaining bits in the mask
90 /// identify processor resources that are part of the group.
91 ///
92 /// Example:
93 ///
94 ///  ResourceA  -- Mask: 0b001
95 ///  ResourceB  -- Mask: 0b010
96 ///  ResourceAB -- Mask: 0b100 U (ResourceA::Mask | ResourceB::Mask) == 0b111
97 ///
98 /// ResourceAB is a processor resource group containing ResourceA and ResourceB.
99 /// Each resource mask uniquely identifies a resource; both ResourceA and
100 /// ResourceB only have one bit set.
101 /// ResourceAB is a group; excluding the most significant bit in the mask, the
102 /// remaining bits identify the composition of the group.
103 ///
104 /// Resource masks are used by the ResourceManager to solve set membership
105 /// problems with simple bit manipulation operations.
106 void computeProcResourceMasks(const MCSchedModel &SM,
107                               MutableArrayRef<uint64_t> Masks);
108 
109 /// Compute the reciprocal block throughput from a set of processor resource
110 /// cycles. The reciprocal block throughput is computed as the MAX between:
111 ///  - NumMicroOps / DispatchWidth
112 ///  - ProcResourceCycles / #ProcResourceUnits  (for every consumed resource).
113 double computeBlockRThroughput(const MCSchedModel &SM, unsigned DispatchWidth,
114                                unsigned NumMicroOps,
115                                ArrayRef<unsigned> ProcResourceUsage);
116 } // namespace mca
117 } // namespace llvm
118 
119 #endif // LLVM_MCA_SUPPORT_H
120