// Construct backward graph.
      auto dz = Const(scope, {{1.0, 1.0}, {1.0, 1.0}});
      auto dx = MatMul(scope, dz, y, MatMul::TransposeB(true));
      auto dy = MatMul(scope, x, dz, MatMul::TransposeA(true));

      auto du = MatMul(scope, dx, v, MatMul::TransposeB(true));
      auto dv = MatMul(scope, u, dx, MatMul::TransposeA(true));
    } else {
      // Call AddSymbolicGradients.

	VPDPWSSD -7(CX)(DX*4), Y2, K3, Y14                 // 62726d2b52b491f9ffffff
	VPDPWSSD Y8, Y22, K3, Y14                          // 62524d2352f0
	VPDPWSSD Y9, Y22, K3, Y14                          // 62524d2352f1
	VPDPWSSD Y22, Y22, K3, Y14                         // 62324d2352f6
	VPDPWSSD 15(R8)(R14*4), Y22, K3, Y14               // 62124d2352b4b00f000000

	{"X%s", "X 27 ", &stringVal, "27"},

	{"X%dX", "X27X", &intVal, 27},
	{"X%dX", "X27 X", &intVal, nil}, // input does not match format
	{"X%dX", "X 27X", &intVal, 27},
	{"X%dX", "X 27 X", &intVal, nil}, // input does not match format

	{"X%dX", "X27X", &intVal, 27},
	{"X%dX", "X27X ", &intVal, 27},
	{"X%dX", " X27X", &intVal, nil},  // input does not match format
	{"X%dX", " X27X ", &intVal, nil}, // input does not match format

	VPSHUFBITQMB 15(DX)(BX*2), X7, K6, K0              // 62f2450e8f845a0f000000
	VPSHUFBITQMB X24, X13, K6, K0                      // 6292150e8fc0
	VPSHUFBITQMB X7, X13, K6, K0                       // 62f2150e8fc7
	VPSHUFBITQMB X0, X13, K6, K0                       // 62f2150e8fc0
	VPSHUFBITQMB (R8), X13, K6, K0                     // 62d2150e8f00
	VPSHUFBITQMB 15(DX)(BX*2), X13, K6, K0             // 62f2150e8f845a0f000000

	VPERMB -7(CX)(DX*8), Y31, K7, Y22                  // 62e205278db4d1f9ffffff
	VPERMB Y5, Y5, K7, Y22                             // 62e2552f8df5
	VPERMB Y19, Y5, K7, Y22                            // 62a2552f8df3
	VPERMB Y31, Y5, K7, Y22                            // 6282552f8df7
	VPERMB 17(SP)(BP*1), Y5, K7, Y22                   // 62e2552f8db42c11000000

	bw := blockWriter{e: e}
	bw.setup()
	lzww := lzw.NewWriter(bw, lzw.LSB, litWidth)
	if dx := b.Dx(); dx == pm.Stride {
		_, e.err = lzww.Write(pm.Pix[:dx*b.Dy()])
		if e.err != nil {
			lzww.Close()
			return
		}
	} else {
		for i, y := 0, b.Min.Y; y < b.Max.Y; i, y = i+pm.Stride, y+1 {
			_, e.err = lzww.Write(pm.Pix[i : i+dx])
			if e.err != nil {
				lzww.Close()
				return
			}
		}
	}

            ["-Dfoo=bar", "-Dfoo2=hey buddy", "-Dfoo3=baz"]

        fromString("  -Dfoo=\" bar \"  ") == ["-Dfoo= bar "]
        fromString("  -Dx=\"\"  -Dy=\"\n\" ") == ["-Dx=", "-Dy=\n"]
        fromString(" \"-Dx= a b c \" -Dy=\" x y z \" ") == ["-Dx= a b c ", "-Dy= x y z "]
    }

    def "understands quoted system properties and jvm opts"() {
        expect:

	MOVL	((index-2)*4)(BP), AX; \
	MOVL	AX, CX; \
	RORL	$17, AX; \
	MOVL	CX, DX; \
	RORL	$19, CX; \
	SHRL	$10, DX; \
	MOVL	((index-15)*4)(BP), BX; \
	XORL	CX, AX; \
	MOVL	BX, CX; \
	XORL	DX, AX; \
	RORL	$7, BX; \
	MOVL	CX, DX; \
	SHRL	$3, DX; \
	RORL	$18, CX; \
	ADDL	((index-7)*4)(BP), AX; \
	XORL	CX, BX; \
	XORL	DX, BX; \
	ADDL	((index-16)*4)(BP), BX; \
	ADDL	BX, AX; \
	MOVL	AX, ((index)*4)(BP)

  for (Node* n : while_ctx->exit_nodes()) dy.push_back(backprops[n]);
  std::vector<Output> dx;
  TF_RETURN_IF_ERROR(AddWhileLoopGradient(while_ctx, while_scope, dy, &dx));

  // Backprop along the in edges to the while loop (i.e. the inputs to the enter
  // nodes)
  DCHECK_EQ(dx.size(), while_ctx->enter_nodes().size());
  for (int i = 0, end = dx.size(); i < end; ++i) {
    Node* enter_node = while_ctx->enter_nodes()[i];

	var nPix []uint8
	dx := m.Bounds().Dx()
	dy := m.Bounds().Dy()
	nPix = make([]uint8, dx*dy)
	offset := 0 // steps through the input by sequential scan lines.
	for _, pass := range interlacing {
		nOffset := pass.start * dx // steps through the output as defined by pass.
		for y := pass.start; y < dy; y += pass.skip {
			copy(nPix[nOffset:nOffset+dx], m.Pix[offset:offset+dx])
			offset += dx