PeepholeOpt: Remove unnecessary check for null TargetInstrInfo (#123929)

This can never happen.

llvm/lib/CodeGen/PeepholeOptimizer.cpp

diff --git a/llvm/lib/CodeGen/PeepholeOptimizer.cpp b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
index 5d76d36..d56f040 100644
--- a/llvm/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
@@ -1991,11 +1991,6 @@
     // turn that into an assertion.
     return ValueTrackerResult();
 
-  if (!TII)
-    // We could handle the REG_SEQUENCE here, but we do not want to
-    // duplicate the code from the generic TII.
-    return ValueTrackerResult();
-
   SmallVector<RegSubRegPairAndIdx, 8> RegSeqInputRegs;
   if (!TII->getRegSequenceInputs(*Def, DefIdx, RegSeqInputRegs))
     return ValueTrackerResult();
@@ -2024,11 +2019,6 @@
     // I.e., this may be turned into an assert.
     return ValueTrackerResult();
 
-  if (!TII)
-    // We could handle the REG_SEQUENCE here, but we do not want to
-    // duplicate the code from the generic TII.
-    return ValueTrackerResult();
-
   RegSubRegPair BaseReg;
   RegSubRegPairAndIdx InsertedReg;
   if (!TII->getInsertSubregInputs(*Def, DefIdx, BaseReg, InsertedReg))
@@ -2078,11 +2068,6 @@
   if (DefSubReg)
     return ValueTrackerResult();
 
-  if (!TII)
-    // We could handle the EXTRACT_SUBREG here, but we do not want to
-    // duplicate the code from the generic TII.
-    return ValueTrackerResult();
-
   RegSubRegPairAndIdx ExtractSubregInputReg;
   if (!TII->getExtractSubregInputs(*Def, DefIdx, ExtractSubregInputReg))
     return ValueTrackerResult();