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Accelerate isel dispatch for tables that start with a top-level

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OPC_SwitchOpcode to use a table lookup instead of having to go
through the interpreter for this.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97469 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-03-01 18:47:11 +00:00
parent d1f94e90fd
commit 7390eebd49
2 changed files with 40 additions and 1 deletions
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4
include/llvm/CodeGen/SelectionDAGISel.h
View File

@ -245,6 +245,10 @@ private:
/// one preferred by the target.
///
ScheduleDAGSDNodes *CreateScheduler();
/// OpcodeOffset - This is a cache used to dispatch efficiently into isel
/// state machines that start with a OPC_SwitchOpcode node.
std::vector<unsigned> OpcodeOffset;
};
}

37
lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
View File

@ -1665,8 +1665,43 @@ SelectCodeCommon(SDNode *NodeToMatch, const unsigned char *MatcherTable,
NodeToMatch->dump(CurDAG);
errs() << '\n');
// Interpreter starts at opcode #0.
// Determine where to start the interpreter. Normally we start at opcode #0,
// but if the state machine starts with an OPC_SwitchOpcode, then we
// accelerate the first lookup (which is guaranteed to be hot) with the
// OpcodeOffset table.
unsigned MatcherIndex = 0;
if (!OpcodeOffset.empty()) {
// Already computed the OpcodeOffset table, just index into it.
if (N.getOpcode() < OpcodeOffset.size())
MatcherIndex = OpcodeOffset[N.getOpcode()];
DEBUG(errs() << " Initial Opcode index to " << MatcherIndex << "\n");
} else if (MatcherTable[0] == OPC_SwitchOpcode) {
// Otherwise, the table isn't computed, but the state machine does start
// with an OPC_SwitchOpcode instruction. Populate the table now, since this
// is the first time we're selecting an instruction.
unsigned Idx = 1;
while (1) {
// Get the size of this case.
unsigned CaseSize = MatcherTable[Idx++];
if (CaseSize & 128)
CaseSize = GetVBR(CaseSize, MatcherTable, Idx);
if (CaseSize == 0) break;
// Get the opcode, add the index to the table.
unsigned Opc = MatcherTable[Idx++];
if (Opc >= OpcodeOffset.size())
OpcodeOffset.resize((Opc+1)*2);
OpcodeOffset[Opc] = Idx;
Idx += CaseSize;
}
// Okay, do the lookup for the first opcode.
if (N.getOpcode() < OpcodeOffset.size())
MatcherIndex = OpcodeOffset[N.getOpcode()];
}
while (1) {
assert(MatcherIndex < TableSize && "Invalid index");
BuiltinOpcodes Opcode = (BuiltinOpcodes)MatcherTable[MatcherIndex++];