I'm introducing a new machine model to simultaneously allow simple

subtarget CPU descriptions and support new features of
MachineScheduler.

MachineModel has three categories of data:
1) Basic properties for coarse grained instruction cost model.
2) Scheduler Read/Write resources for simple per-opcode and operand cost model (TBD).
3) Instruction itineraties for detailed per-cycle reservation tables.

These will all live side-by-side. Any subtarget can use any
combination of them. Instruction itineraries will not change in the
near term. In the long run, I expect them to only be relevant for
in-order VLIW machines that have complex contraints and require a
precise scheduling/bundling model. Once itineraries are only actively
used by VLIW-ish targets, they could be replaced by something more
appropriate for those targets.

This tablegen backend rewrite sets things up for introducing
MachineModel type #2: per opcode/operand cost model.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159891 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 5 deletions

diff --git a/lib/Target/ARM/ARMScheduleA8.td b/lib/Target/ARM/ARMScheduleA8.td
index 61de00a208..56197d4e00 100644
--- a/lib/Target/ARM/ARMScheduleA8.td
+++ b/lib/Target/ARM/ARMScheduleA8.td
@@ -22,11 +22,7 @@ def A8_NLSPipe : FuncUnit; // NEON LS pipe
 //
 // Dual issue pipeline represented by A8_Pipe0 | A8_Pipe1
 //
-def CortexA8Itineraries : MultiIssueItineraries<
-  2,  // IssueWidth
-  -1, // MinLatency - OperandCycles are interpreted as MinLatency.
-  2,  // LoadLatency - overriden by OperandCycles.
-  10, // HighLatency - currently unused.
+def CortexA8Itineraries : ProcessorItineraries<
   [A8_Pipe0, A8_Pipe1, A8_LSPipe, A8_NPipe, A8_NLSPipe],
   [], [
   // Two fully-pipelined integer ALU pipelines
@@ -1061,3 +1057,18 @@ def CortexA8Itineraries : MultiIssueItineraries<
                                InstrStage<1, [A8_NPipe], 0>,
                             InstrStage<2, [A8_NLSPipe]>], [4, 1, 2, 2, 3, 3, 1]>
 ]>;
+
+// ===---------------------------------------------------------------------===//
+// This following definitions describe the simple machine model which
+// will replace itineraries.
+
+// Cortex-A8 machine model for scheduling and other instruction cost heuristics.
+def CortexA8Model : SchedMachineModel {
+  let IssueWidth = 2; // 2 micro-ops are dispatched per cycle.
+  let MinLatency = -1; // OperandCycles are interpreted as MinLatency.
+  let LoadLatency = 2; // Optimistic load latency assuming bypass.
+                       // This is overriden by OperandCycles if the
+                       // Itineraries are queried instead.
+
+  let Itineraries = CortexA8Itineraries;
+}