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1 //===--------------------- Support.cpp --------------------------*- 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 /// This file implements a few helper functions used by various pipeline
12 /// components.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #include "Support.h"
17 #include "llvm/MC/MCSchedule.h"
18 
19 namespace mca {
20 
21 using namespace llvm;
22 
computeProcResourceMasks(const MCSchedModel & SM,SmallVectorImpl<uint64_t> & Masks)23 void computeProcResourceMasks(const MCSchedModel &SM,
24                               SmallVectorImpl<uint64_t> &Masks) {
25   unsigned ProcResourceID = 0;
26 
27   // Create a unique bitmask for every processor resource unit.
28   // Skip resource at index 0, since it always references 'InvalidUnit'.
29   Masks.resize(SM.getNumProcResourceKinds());
30   for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) {
31     const MCProcResourceDesc &Desc = *SM.getProcResource(I);
32     if (Desc.SubUnitsIdxBegin)
33       continue;
34     Masks[I] = 1ULL << ProcResourceID;
35     ProcResourceID++;
36   }
37 
38   // Create a unique bitmask for every processor resource group.
39   for (unsigned I = 1, E = SM.getNumProcResourceKinds(); I < E; ++I) {
40     const MCProcResourceDesc &Desc = *SM.getProcResource(I);
41     if (!Desc.SubUnitsIdxBegin)
42       continue;
43     Masks[I] = 1ULL << ProcResourceID;
44     for (unsigned U = 0; U < Desc.NumUnits; ++U) {
45       uint64_t OtherMask = Masks[Desc.SubUnitsIdxBegin[U]];
46       Masks[I] |= OtherMask;
47     }
48     ProcResourceID++;
49   }
50 }
51 
computeBlockRThroughput(const MCSchedModel & SM,unsigned DispatchWidth,unsigned NumMicroOps,ArrayRef<unsigned> ProcResourceUsage)52 double computeBlockRThroughput(const MCSchedModel &SM, unsigned DispatchWidth,
53                                unsigned NumMicroOps,
54                                ArrayRef<unsigned> ProcResourceUsage) {
55   // The block throughput is bounded from above by the hardware dispatch
56   // throughput. That is because the DispatchWidth is an upper bound on the
57   // number of opcodes that can be part of a single dispatch group.
58   double Max = static_cast<double>(NumMicroOps) / DispatchWidth;
59 
60   // The block throughput is also limited by the amount of hardware parallelism.
61   // The number of available resource units affects the resource pressure
62   // distribution, as well as how many blocks can be executed every cycle.
63   for (unsigned I = 0, E = SM.getNumProcResourceKinds(); I < E; ++I) {
64     unsigned ResourceCycles = ProcResourceUsage[I];
65     if (!ResourceCycles)
66       continue;
67 
68     const MCProcResourceDesc &MCDesc = *SM.getProcResource(I);
69     double Throughput = static_cast<double>(ResourceCycles) / MCDesc.NumUnits;
70     Max = std::max(Max, Throughput);
71   }
72 
73   // The block reciprocal throughput is computed as the MAX of:
74   //  - (NumMicroOps / DispatchWidth)
75   //  - (NumUnits / ResourceCycles)   for every consumed processor resource.
76   return Max;
77 }
78 
79 } // namespace mca
80