The `ant.importBuild()` method also handles `<ant>` and `<antcall>` tasks transparently, which allows for a phased migration.

The following steps highlight a suggested method for migrating a multi-project build:

func (p *Package) rewriteCalls(f *File) bool {
	needsUnsafe := false
	// Walk backward so that in C.f1(C.f2()) we rewrite C.f2 first.
	for _, call := range f.Calls {
		if call.Done {
			continue
		}
		start := f.offset(call.Call.Pos())
		end := f.offset(call.Call.End())
		str, nu := p.rewriteCall(f, call)
		if str != "" {
			f.Edit.Replace(start, end, str)
			if nu {
				needsUnsafe = true
			}
		}
	}

  return success();
}

void LegacyCallOp::setCalleeFromCallable(mlir::CallInterfaceCallable callee) {
  // Direct call.
  if (SymbolRefAttr fAttr = getFAttr()) {
    SymbolRefAttr calleeAttr = callee.get<SymbolRefAttr>();
    return setFAttr(cast<FlatSymbolRefAttr>(calleeAttr));
  }
  // Indirect call, callee Value is the first operand.
  return setOperand(0, callee.get<Value>());
}

	}
	r, li := l.toLocal(i)
	return r.Sym(li).IsPkgInit()
}

// Return whether this is a trampoline of a deferreturn call.
func (l *Loader) IsDeferReturnTramp(i Sym) bool {
	return l.deferReturnTramp[i]
}

// Set that i is a trampoline of a deferreturn call.
func (l *Loader) SetIsDeferReturnTramp(i Sym, v bool) {
	l.deferReturnTramp[i] = v
}

(Zero (SelectN [0] call:(StaticLECall _ _)) mem:(SelectN [1] call))
	&& isSameCall(call.Aux, "runtime.newobject")
	=> mem

(Store (SelectN [0] call:(StaticLECall _ _)) x mem:(SelectN [1] call))
	&& isConstZero(x)
	&& isSameCall(call.Aux, "runtime.newobject")
	=> mem

(Store (OffPtr (SelectN [0] call:(StaticLECall _ _))) x mem:(SelectN [1] call))
	&& isConstZero(x)

	case 76: // set program mask
		zRR(op_SPM, uint32(p.From.Reg), 0, asm)

	case 77: // syscall $constant
		if p.From.Offset > 255 || p.From.Offset < 1 {
			c.ctxt.Diag("illegal system call; system call number out of range: %v", p)
			zE(op_TRAP2, asm) // trap always
		} else {
			zI(op_SVC, uint32(p.From.Offset), asm)
		}

	case 78: // undef

        requires all optimizer variables to be created at the first
        `apply_gradients()` or `minimize()` call. If your workflow calls
        optimizer to update different parts of model in multiple stages,
        please call `optimizer.build(model.trainable_variables)` before the
        training loop.
    *   **Performance regression on `ParameterServerStrategy`.** This could be