1 //===- MipsAnalyzeImmediate.cpp - Analyze Immediates ----------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "MipsAnalyzeImmediate.h"
12 #include "llvm/Support/MathExtras.h"
19 MipsAnalyzeImmediate::Inst::Inst(unsigned O, unsigned I) : Opc(O), ImmOpnd(I) {}
21 // Add I to the instruction sequences.
22 void MipsAnalyzeImmediate::AddInstr(InstSeqLs &SeqLs, const Inst &I) {
23 // Add an instruction seqeunce consisting of just I.
25 SeqLs.push_back(InstSeq(1, I));
29 for (InstSeqLs::iterator Iter = SeqLs.begin(); Iter != SeqLs.end(); ++Iter)
33 void MipsAnalyzeImmediate::GetInstSeqLsADDiu(uint64_t Imm, unsigned RemSize,
35 GetInstSeqLs((Imm + 0x8000ULL) & 0xffffffffffff0000ULL, RemSize, SeqLs);
36 AddInstr(SeqLs, Inst(ADDiu, Imm & 0xffffULL));
39 void MipsAnalyzeImmediate::GetInstSeqLsORi(uint64_t Imm, unsigned RemSize,
41 GetInstSeqLs(Imm & 0xffffffffffff0000ULL, RemSize, SeqLs);
42 AddInstr(SeqLs, Inst(ORi, Imm & 0xffffULL));
45 void MipsAnalyzeImmediate::GetInstSeqLsSLL(uint64_t Imm, unsigned RemSize,
47 unsigned Shamt = countTrailingZeros(Imm);
48 GetInstSeqLs(Imm >> Shamt, RemSize - Shamt, SeqLs);
49 AddInstr(SeqLs, Inst(SLL, Shamt));
52 void MipsAnalyzeImmediate::GetInstSeqLs(uint64_t Imm, unsigned RemSize,
54 uint64_t MaskedImm = Imm & (0xffffffffffffffffULL >> (64 - Size));
56 // Do nothing if Imm is 0.
60 // A single ADDiu will do if RemSize <= 16.
62 AddInstr(SeqLs, Inst(ADDiu, MaskedImm));
66 // Shift if the lower 16-bit is cleared.
67 if (!(Imm & 0xffff)) {
68 GetInstSeqLsSLL(Imm, RemSize, SeqLs);
72 GetInstSeqLsADDiu(Imm, RemSize, SeqLs);
74 // If bit 15 is cleared, it doesn't make a difference whether the last
75 // instruction is an ADDiu or ORi. In that case, do not call GetInstSeqLsORi.
78 GetInstSeqLsORi(Imm, RemSize, SeqLsORi);
79 SeqLs.append(std::make_move_iterator(SeqLsORi.begin()),
80 std::make_move_iterator(SeqLsORi.end()));
84 // Replace a ADDiu & SLL pair with a LUi.
85 // e.g. the following two instructions
90 void MipsAnalyzeImmediate::ReplaceADDiuSLLWithLUi(InstSeq &Seq) {
91 // Check if the first two instructions are ADDiu and SLL and the shift amount
93 if ((Seq.size() < 2) || (Seq[0].Opc != ADDiu) ||
94 (Seq[1].Opc != SLL) || (Seq[1].ImmOpnd < 16))
97 // Sign-extend and shift operand of ADDiu and see if it still fits in 16-bit.
98 int64_t Imm = SignExtend64<16>(Seq[0].ImmOpnd);
99 int64_t ShiftedImm = (uint64_t)Imm << (Seq[1].ImmOpnd - 16);
101 if (!isInt<16>(ShiftedImm))
104 // Replace the first instruction and erase the second.
106 Seq[0].ImmOpnd = (unsigned)(ShiftedImm & 0xffff);
107 Seq.erase(Seq.begin() + 1);
110 void MipsAnalyzeImmediate::GetShortestSeq(InstSeqLs &SeqLs, InstSeq &Insts) {
111 InstSeqLs::iterator ShortestSeq = SeqLs.end();
112 // The length of an instruction sequence is at most 7.
113 unsigned ShortestLength = 8;
115 for (InstSeqLs::iterator S = SeqLs.begin(); S != SeqLs.end(); ++S) {
116 ReplaceADDiuSLLWithLUi(*S);
117 assert(S->size() <= 7);
119 if (S->size() < ShortestLength) {
121 ShortestLength = S->size();
126 Insts.append(ShortestSeq->begin(), ShortestSeq->end());
129 const MipsAnalyzeImmediate::InstSeq
130 &MipsAnalyzeImmediate::Analyze(uint64_t Imm, unsigned Size,
131 bool LastInstrIsADDiu) {
140 ADDiu = Mips::DADDiu;
148 // Get the list of instruction sequences.
149 if (LastInstrIsADDiu | !Imm)
150 GetInstSeqLsADDiu(Imm, Size, SeqLs);
152 GetInstSeqLs(Imm, Size, SeqLs);
154 // Set Insts to the shortest instruction sequence.
155 GetShortestSeq(SeqLs, Insts);