[llvm] [MacroFusion] Add SingleFusion that accepts a single instruction pair (PR #85630)

[Matt Arsenault via llvm-commits]

================
@@ -1879,3 +1879,8 @@ include "llvm/Target/GlobalISel/SelectionDAGCompat.td"
 // Pull in the common support for Pfm Counters generation.
 //
 include "llvm/Target/TargetPfmCounters.td"
+
+//===----------------------------------------------------------------------===//
+// Pull in the common support for macro fusion.
+//
+include "llvm/Target/TargetMacroFusion.td"
----------------
arsenm wrote:

Separately commit the move-to-separate-file part?

https://github.com/llvm/llvm-project/pull/85630