Make NumMicroOps a variable in the subtarget's instruction itinerary.

The TargetInstrInfo::getNumMicroOps API does not change, but soon it
will be used by MachineScheduler. Now each subtarget can specify the
number of micro-ops per itinerary class. For ARM, this is currently
always dynamic (-1), because it is used for load/store multiple which
depends on the number of register operands.

Zero is now a valid number of micro-ops. This can be used for
nop pseudo-instructions or instructions that the hardware can squash
during dispatch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159406 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 1 deletions

diff --git a/include/llvm/Target/TargetInstrInfo.h b/include/llvm/Target/TargetInstrInfo.h
index 4e73139..87f1fe5 100644
--- a/include/llvm/Target/TargetInstrInfo.h
+++ b/include/llvm/Target/TargetInstrInfo.h
@@ -648,7 +648,9 @@ public:
   }
 
   /// getNumMicroOps - Return the number of u-operations the given machine
-  /// instruction will be decoded to on the target cpu.
+  /// instruction will be decoded to on the target cpu. The itinerary's
+  /// IssueWidth is the number of microops that can be dispatched each
+  /// cycle. An instruction with zero microops takes no dispatch resources.
   virtual unsigned getNumMicroOps(const InstrItineraryData *ItinData,
                                   const MachineInstr *MI) const = 0;