Accelerate isel dispatch for tables that start with a top-level
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
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 03cbe22..3c5e90b 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -1665,8 +1665,43 @@
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++];