[CodeGen] Use range-based for loops (NFC) (#138488)

This is a reland of #138434 except that:

- the bits for llvm/lib/CodeGen/RenameIndependentSubregs.cpp
  have been dropped because they caused a test failure under asan, and

- the bits for llvm/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp have
  been improved with structured bindings.

1 files changed, 4 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/MachineCSE.cpp b/llvm/lib/CodeGen/MachineCSE.cpp
index 6d14509..bebdead 100644
--- a/llvm/lib/CodeGen/MachineCSE.cpp
+++ b/llvm/lib/CodeGen/MachineCSE.cpp
@@ -325,9 +325,8 @@ bool MachineCSEImpl::hasLivePhysRegDefUses(const MachineInstr *MI,
   }
 
   // Finally, add all defs to PhysRefs as well.
-  for (unsigned i = 0, e = PhysDefs.size(); i != e; ++i)
-    for (MCRegAliasIterator AI(PhysDefs[i].second, TRI, true); AI.isValid();
-         ++AI)
+  for (const auto &Def : PhysDefs)
+    for (MCRegAliasIterator AI(Def.second, TRI, true); AI.isValid(); ++AI)
       PhysRefs.insert(*AI);
 
   return !PhysRefs.empty();
@@ -348,9 +347,8 @@ bool MachineCSEImpl::PhysRegDefsReach(MachineInstr *CSMI, MachineInstr *MI,
     if (MBB->pred_size() != 1 || *MBB->pred_begin() != CSMBB)
       return false;
 
-    for (unsigned i = 0, e = PhysDefs.size(); i != e; ++i) {
-      if (MRI->isAllocatable(PhysDefs[i].second) ||
-          MRI->isReserved(PhysDefs[i].second))
+    for (const auto &PhysDef : PhysDefs) {
+      if (MRI->isAllocatable(PhysDef.second) || MRI->isReserved(PhysDef.second))
         // Avoid extending live range of physical registers if they are
         //allocatable or reserved.
         return false;