[llvm] [ScheduleDAG] Remove obsolete VReg2SUnitMap. NFC (PR #96559)

[Björn Pettersson via llvm-commits]

https://github.com/bjope created https://github.com/llvm/llvm-project/pull/96559

The VReg2SUnitMap type is not used anywhere (it has probably been obsolete since commit 97d0ffbe0647c4ec49ed4 back in 2015). This commit simply removes the type definition.

>From 5e0e538fb3b8756f2ca72be8d3a65b2b267b8a0f Mon Sep 17 00:00:00 2001
From: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
Date: Thu, 20 Jun 2024 14:14:44 +0200
Subject: [PATCH] [ScheduleDAG] Remove obsolete VReg2SUnitMap. NFC

The VReg2SUnitMap type is not used anywhere (it has probably been
obsolete since commit 97d0ffbe0647c4ec49ed4 back in 2015).
This commit simply removes the type definition.
---
 llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h b/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h
index 32ff15fc75936..822b06f080fa6 100644
--- a/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h
+++ b/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h
@@ -18,7 +18,6 @@
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/SparseMultiSet.h"
-#include "llvm/ADT/SparseSet.h"
 #include "llvm/ADT/identity.h"
 #include "llvm/CodeGen/LiveRegUnits.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
@@ -91,12 +90,6 @@ namespace llvm {
   using RegUnit2SUnitsMap =
       SparseMultiSet<PhysRegSUOper, identity<unsigned>, uint16_t>;
 
-  /// Use SparseSet as a SparseMap by relying on the fact that it never
-  /// compares ValueT's, only unsigned keys. This allows the set to be cleared
-  /// between scheduling regions in constant time as long as ValueT does not
-  /// require a destructor.
-  using VReg2SUnitMap = SparseSet<VReg2SUnit, VirtReg2IndexFunctor>;
-
   /// Track local uses of virtual registers. These uses are gathered by the DAG
   /// builder and may be consulted by the scheduler to avoid iterating an entire
   /// vreg use list.