1 //===-- HexagonTargetTransformInfo.cpp - Hexagon specific TTI pass --------===//
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 /// \file
9 /// This file implements a TargetTransformInfo analysis pass specific to the
10 /// Hexagon target machine. It uses the target's detailed information to provide
11 /// more precise answers to certain TTI queries, while letting the target
12 /// independent and default TTI implementations handle the rest.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #include "HexagonTargetTransformInfo.h"
17 #include "llvm/IR/Instructions.h"
18 #include "llvm/Support/Debug.h"
19 
20 using namespace llvm;
21 
22 #define DEBUG_TYPE "hexagontti"
23 
24 static cl::opt<bool> EmitLookupTables("hexagon-emit-lookup-tables",
25   cl::init(true), cl::Hidden,
26   cl::desc("Control lookup table emission on Hexagon target"));
27 
28 TargetTransformInfo::PopcntSupportKind
29 HexagonTTIImpl::getPopcntSupport(unsigned IntTyWidthInBit) const {
30   // Return Fast Hardware support as every input  < 64 bits will be promoted
31   // to 64 bits.
32   return TargetTransformInfo::PSK_FastHardware;
33 }
34 
35 // The Hexagon target can unroll loops with run-time trip counts.
36 void HexagonTTIImpl::getUnrollingPreferences(Loop *L, ScalarEvolution &SE,
37                                              TTI::UnrollingPreferences &UP) {
38   UP.Runtime = UP.Partial = true;
39 }
40 
41 unsigned HexagonTTIImpl::getNumberOfRegisters(bool vector) const {
42   return vector ? 0 : 32;
43 }
44 
45 unsigned HexagonTTIImpl::getPrefetchDistance() const {
46   return getST()->getL1PrefetchDistance();
47 }
48 
49 unsigned HexagonTTIImpl::getCacheLineSize() const {
50   return getST()->getL1CacheLineSize();
51 }
52 
53 int HexagonTTIImpl::getUserCost(const User *U,
54                                 ArrayRef<const Value *> Operands) {
55   auto isCastFoldedIntoLoad = [](const CastInst *CI) -> bool {
56     if (!CI->isIntegerCast())
57       return false;
58     const LoadInst *LI = dyn_cast<const LoadInst>(CI->getOperand(0));
59     // Technically, this code could allow multiple uses of the load, and
60     // check if all the uses are the same extension operation, but this
61     // should be sufficient for most cases.
62     if (!LI || !LI->hasOneUse())
63       return false;
64 
65     // Only extensions from an integer type shorter than 32-bit to i32
66     // can be folded into the load.
67     unsigned SBW = CI->getSrcTy()->getIntegerBitWidth();
68     unsigned DBW = CI->getDestTy()->getIntegerBitWidth();
69     return DBW == 32 && (SBW < DBW);
70   };
71 
72   if (const CastInst *CI = dyn_cast<const CastInst>(U))
73     if (isCastFoldedIntoLoad(CI))
74       return TargetTransformInfo::TCC_Free;
75   return BaseT::getUserCost(U, Operands);
76 }
77 
78 bool HexagonTTIImpl::shouldBuildLookupTables() const {
79    return EmitLookupTables;
80 }
81