[NFC][Verifier] Remove checks for atomic loads/stores that alignment is non-zero

[aeubanks]

Summary

The alignment is never 0 since getAlign() returns 1 << bits.

[dexonsmith]

Nice! LGTM.

llvm/lib/IR/Verifier.cpp

void Verifier::visitLoadInst(LoadInst &LI) {
   Type *ElTy = LI.getType();
   Assert(LI.getAlignment() <= Value::MaximumAlignment,
          "huge alignment values are unsupported", &LI);
   Assert(ElTy->isSized(), "loading unsized types is not allowed", &LI);
   if (LI.isAtomic()) {
     Assert(LI.getOrdering() != AtomicOrdering::Release &&
                LI.getOrdering() != AtomicOrdering::AcquireRelease,
            "Load cannot have Release ordering", &LI);
-    Assert(LI.getAlignment() != 0,
-           "Atomic load must specify explicit alignment", &LI);
     Assert(ElTy->isIntOrPtrTy() || ElTy->isFloatingPointTy(),
            "atomic load operand must have integer, pointer, or floating point "
            "type!",
            ElTy, &LI);
     checkAtomicMemAccessSize(ElTy, &LI);
   } else {
     Assert(LI.getSyncScopeID() == SyncScope::System,
            "Non-atomic load cannot have SynchronizationScope specified", &LI);
Assert(PTy->isOpaqueOrPointeeTypeMatches(ElTy),
          "Stored value type does not match pointer operand type!", &SI, ElTy);
   Assert(SI.getAlignment() <= Value::MaximumAlignment,
          "huge alignment values are unsupported", &SI);
   Assert(ElTy->isSized(), "storing unsized types is not allowed", &SI);
   if (SI.isAtomic()) {
     Assert(SI.getOrdering() != AtomicOrdering::Acquire &&
                SI.getOrdering() != AtomicOrdering::AcquireRelease,
            "Store cannot have Acquire ordering", &SI);
-    Assert(SI.getAlignment() != 0,
-           "Atomic store must specify explicit alignment", &SI);
     Assert(ElTy->isIntOrPtrTy() || ElTy->isFloatingPointTy(),
            "atomic store operand must have integer, pointer, or floating point "
            "type!",
            ElTy, &SI);
     checkAtomicMemAccessSize(ElTy, &SI);
   } else {
     Assert(SI.getSyncScopeID() == SyncScope::System,
            "Non-atomic store cannot have SynchronizationScope specified", &SI);