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 TargetTransformInfo::PopcntSupportKind
25 HexagonTTIImpl::getPopcntSupport(unsigned IntTyWidthInBit) const {
26   // Return Fast Hardware support as every input  < 64 bits will be promoted
27   // to 64 bits.
28   return TargetTransformInfo::PSK_FastHardware;
29 }
30 
31 // The Hexagon target can unroll loops with run-time trip counts.
32 void HexagonTTIImpl::getUnrollingPreferences(Loop *L,
33                                              TTI::UnrollingPreferences &UP) {
34   UP.Runtime = UP.Partial = true;
35 }
36 
37 unsigned HexagonTTIImpl::getNumberOfRegisters(bool vector) const {
38   return vector ? 0 : 32;
39 }
40 
41 unsigned HexagonTTIImpl::getPrefetchDistance() const {
42   return getST()->getL1PrefetchDistance();
43 }
44 
45 unsigned HexagonTTIImpl::getCacheLineSize() const {
46   return getST()->getL1CacheLineSize();
47 }
48 
49 int HexagonTTIImpl::getUserCost(const User *U) {
50   auto isCastFoldedIntoLoad = [] (const CastInst *CI) -> bool {
51     if (!CI->isIntegerCast())
52       return false;
53     const LoadInst *LI = dyn_cast<const LoadInst>(CI->getOperand(0));
54     // Technically, this code could allow multiple uses of the load, and
55     // check if all the uses are the same extension operation, but this
56     // should be sufficient for most cases.
57     if (!LI || !LI->hasOneUse())
58       return false;
59 
60     // Only extensions from an integer type shorter than 32-bit to i32
61     // can be folded into the load.
62     unsigned SBW = CI->getSrcTy()->getIntegerBitWidth();
63     unsigned DBW = CI->getDestTy()->getIntegerBitWidth();
64     return DBW == 32 && (SBW < DBW);
65   };
66 
67   if (const CastInst *CI = dyn_cast<const CastInst>(U))
68     if (isCastFoldedIntoLoad(CI))
69       return TargetTransformInfo::TCC_Free;
70   return BaseT::getUserCost(U);
71 }
72