N, _ := NewModulusFromBig(n)
	A := NewNat().setBig(a).ExpandFor(N)
	B := NewNat().setBig(b).ExpandFor(N)

	if A.Mul(B, N).IsZero() != 1 {
		t.Error("a * b mod (a * b) != 0")
	}

	i := new(big.Int).ModInverse(a, b)
	N, _ = NewModulusFromBig(b)
	A = NewNat().setBig(a).ExpandFor(N)
	I := NewNat().setBig(i).ExpandFor(N)
	one := NewNat().setBig(big.NewInt(1)).ExpandFor(N)

	if A.Mul(I, N).Equal(one) != 1 {

		}
	}
}

func testDeferPtrsGoexit(c chan int, i int) {
	var y int
	defer func() {
		c <- y
	}()
	defer setBig(&y, 42, bigBuf{})
	useStackAndCall(i, Goexit)
}

func setBig(p *int, x int, b bigBuf) {
	*p = x
}

// TestDeferPtrsPanic is like TestDeferPtrsGoexit, but it's using panic instead

func (x *Nat) set(y *Nat) *Nat {
	x.reset(len(y.limbs))
	copy(x.limbs, y.limbs)
	return x
}

// setBig assigns x = n, optionally resizing n to the appropriate size.
//
// The announced length of x is set based on the actual bit size of the input,
// ignoring leading zeroes.
func (x *Nat) setBig(n *big.Int) *Nat {
	limbs := n.Bits()
	x.reset(len(limbs))
	for i := range limbs {
		x.limbs[i] = uint(limbs[i])

	case TFLOAT32:
		w = 4
		t.floatRegs = 1
		t.setAlg(AFLOAT32)

	case TFLOAT64:
		w = 8
		t.align = uint8(RegSize)
		t.floatRegs = 1
		t.setAlg(AFLOAT64)

	case TCOMPLEX64:
		w = 8
		t.align = 4
		t.floatRegs = 2
		t.setAlg(ACPLX64)

	case TCOMPLEX128:
		w = 16
		t.align = uint8(RegSize)
		t.floatRegs = 2
		t.setAlg(ACPLX128)

	case TPTR:
		w = int64(PtrSize)

	var uc ucontextt
	getcontext(unsafe.Pointer(&uc))

	// _UC_SIGMASK does not seem to work here.
	// It would be nice if _UC_SIGMASK and _UC_STACK
	// worked so that we could do all the work setting
	// the sigmask and the stack here, instead of setting
	// the mask here and the stack in netbsdMstart.
	// For now do the blocking manually.
	uc.uc_flags = _UC_SIGMASK | _UC_CPU
	uc.uc_link = nil
	uc.uc_sigmask = sigset_all

		// it may hit stack split that is not expected here.
		if gp != nil {
			setg(nil)
		}
		badsignal(uintptr(sig), c)
		// Restore g
		if gp != nil {
			setg(gp)
		}
		return
	}

	setg(gp.m.gsignal)

	// If some non-Go code called sigaltstack, adjust.
	var gsignalStack gsignalStack

        assertTrue(ZERO.setBit(result).compareTo(x) <= 0);
        assertTrue(ZERO.setBit(result + 1).compareTo(x) > 0);
      }
    }
  }

  public void testLog2Ceiling() {
    for (BigInteger x : POSITIVE_BIGINTEGER_CANDIDATES) {
      for (RoundingMode mode : asList(CEILING, UP)) {
        int result = BigIntegerMath.log2(x, mode);
        assertTrue(ZERO.setBit(result).compareTo(x) >= 0);

}

// See os_freebsd2.go, os_freebsd_amd64.go for setsig function

//go:nosplit
//go:nowritebarrierrec
func setsigstack(i uint32) {
	var sa sigactiont
	sigaction(i, nil, &sa)
	if sa.sa_flags&_SA_ONSTACK != 0 {
		return
	}
	sa.sa_flags |= _SA_ONSTACK
	sigaction(i, &sa, nil)
}

//go:nosplit
//go:nowritebarrierrec
func getsig(i uint32) uintptr {
	var sa sigactiont

				if p.Controls[0] != a {
					continue
				}
				if e.i == 0 {
					if ct == nil {
						ct = f.ConstBool(f.Config.Types.Bool, true)
					}
					v.SetArg(i, ct)
				} else {
					if cf == nil {
						cf = f.ConstBool(f.Config.Types.Bool, false)
					}
					v.SetArg(i, cf)
				}
			}
		}
	}

	// Step 2: Redirect control flow around known branches.
	// p:
	//   ... goto b ...
	// b: <- p ...

	_SIG_SETMASK = 3
	_SS_DISABLE  = 4
)

//extern SigTabTT runtime·sigtab[];

type sigset uint32

var sigset_all = ^sigset(0)

//go:nosplit
//go:nowritebarrierrec
func setsig(i uint32, fn uintptr) {
	var sa usigactiont
	sa.sa_flags = _SA_SIGINFO | _SA_ONSTACK | _SA_RESTART
	sa.sa_mask = ^uint32(0)